Bugs when DECDIG == uint16_t

[mrkn]

Some tests fail when DECDIG is uint16_t.

Failure: test_BigDecimal(TestBigDecimal):
  Expected 0.1e1111111111111111112 to be positive infinite.
  <nil> is not true.
/home/mrkn/src/github.com/ruby/bigdecimal/test/lib/core_assertions.rb:504:in `assert'
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:47:in `assert_positive_infinite'
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:86:in `block in test_BigDecimal'
     83:       BigDecimal.mode(BigDecimal::EXCEPTION_OVERFLOW, false)
     84:       BigDecimal.mode(BigDecimal::EXCEPTION_NaN, false)
     85:       assert_positive_infinite(BigDecimal("Infinity"))
  => 86:       assert_positive_infinite(BigDecimal("1E1111111111111111111"))
     87:       assert_positive_infinite(BigDecimal(" \t\n\r \rInfinity \t\n\r \r"))
     88:       assert_negative_infinite(BigDecimal("-Infinity"))
     89:       assert_negative_infinite(BigDecimal(" \t\n\r \r-Infinity \t\n\r \r"))
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:82:in `save_exception_mode'
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:82:in `test_BigDecimal'

Failure: test_div(TestBigDecimal)
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:956:in `test_div'
     953:     assert_equal(2, BigDecimal("2") / 1)
     954:     assert_equal(-2, BigDecimal("2") / -1)
     955:
  => 956:     assert_equal(BigDecimal('1486.868686869'), BigDecimal('1472.0') / BigDecimal('0.99'), '[ruby-core:59365] [#9316]')
     957:
     958:     assert_equal(4.124045235, BigDecimal('0.9932') / (700 * BigDecimal('0.344045') / BigDecimal('1000.0')), '[#9305]')
     959:
[ruby-core:59365] [#9316]
<0.1486868686869e4> expected but was
<0.14868687e4>

diff:
? 0.1486868686869e4
?          7
?          ??????

Failure: test_power_of_three(TestBigDecimal)
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:1457:in `test_power_of_three'
     1454:   def test_power_of_three
     1455:     x = BigDecimal(3)
     1456:     assert_equal(81, x ** 4)
  => 1457:     assert_equal(1.quo(81), x ** -4)
     1458:     assert_in_delta(1.0/81, x ** -4)
     1459:   end
     1460:
<1/81> expected but was
<0.12345679012345679012345679e-1>

diff:
?   1/8      1
? 0. 23456790 2345679012345679e-1
? ++ ?? +++++++++++++++++++

Failure: test_power_without_prec(TestBigDecimal)
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:1554:in `test_power_without_prec'
     1551:     pi  = BigDecimal("3.14159265358979323846264338327950288419716939937511")
     1552:     e   = BigDecimal("2.71828182845904523536028747135266249775724709369996")
     1553:     pow = BigDecimal("0.2245915771836104547342715220454373502758931513399678438732330680117143493477164265678321738086407229773690574073268002736527e2")
  => 1554:     assert_equal(pow, pi.power(e))
     1555:
     1556:     n = BigDecimal("2222")
     1557:     assert_equal(BigDecimal("0.5171353084572525892492416e12"), (n ** 3.5))
<0.2245915771836104547342715220454373502758931513399678438732330680117143493477164265678321738086407229773690574073268002736527e2> expected but was
<0.2245915771836104547342715220454373502758931513399678438732330680117143493477164265678321738086407229773690574073e2>

diff:
? 0.2245915771836104547342715220454373502758931513399678438732330680117143493477164265678321738086407229773690574073268002736527e2

Error: test_to_f(TestBigDecimal):
  Test::Unit::CoreAssertions::MiniTest::Assertion: 1e-322.
  Exception raised:
  <#<FloatDomainError: BigDecimal to Float conversion>>
  Backtrace:
    /home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:788:in `to_f'
    /home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:788:in `block in test_to_f'
    /home/mrkn/src/github.com/ruby/bigdecimal/test/lib/core_assertions.rb:185:in `assert_nothing_raised'
    /home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:787:in `test_to_f'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testcase.rb:866:in `run_test'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testcase.rb:561:in `block (2 levels) in run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/fixture.rb:276:in `block in create_fixtures_runner'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/fixture.rb:276:in `block in create_fixtures_runner'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/fixture.rb:257:in `run_fixture'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/fixture.rb:292:in `run_setup'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testcase.rb:559:in `block in run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testcase.rb:558:in `catch'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testcase.rb:558:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testsuite.rb:124:in `run_test'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testsuite.rb:53:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testsuite.rb:124:in `run_test'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/testsuite.rb:53:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnermediator.rb:67:in `run_suite'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnermediator.rb:45:in `block (2 levels) in run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnermediator.rb:102:in `with_listener'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnermediator.rb:41:in `block in run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnermediator.rb:39:in `catch'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnermediator.rb:39:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunner.rb:40:in `start_mediator'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunner.rb:25:in `start'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/ui/testrunnerutilities.rb:24:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/autorunner.rb:458:in `block in run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/autorunner.rb:514:in `change_work_directory'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/autorunner.rb:457:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit/autorunner.rb:66:in `run'
    /home/mrkn/.rbenv/versions/3.0.2/lib/ruby/gems/3.0.0/gems/test-unit-3.5.1/lib/test/unit.rb:518:in `block (2 levels) in <top (required)>'.
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:788:in `to_f'
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:788:in `block in test_to_f'
     785:     assert_raise(FloatDomainError, x) {BigDecimal(x).to_f}
     786:     x = "1e#{Float::MIN_10_EXP - Float::DIG}"
     787:     assert_nothing_raised(FloatDomainError, x) {
  => 788:       assert_in_delta(0.0, BigDecimal(x).to_f, 10**Float::MIN_10_EXP, bug6944)
     789:     }
     790:     x = "-#{x}"
     791:     assert_nothing_raised(FloatDomainError, x) {
/home/mrkn/src/github.com/ruby/bigdecimal/test/lib/core_assertions.rb:185:in `assert_nothing_raised'
/home/mrkn/src/github.com/ruby/bigdecimal/test/bigdecimal/test_bigdecimal.rb:787:in `test_to_f'