Support stateful allocators

[aleden]

If one uses boost::interprocess::allocator (or some other stateful allocator) compilation will fail in non-release mode (i.e. !defined(NDEBUG)) on two methods of dynamic_bitset (move constructor and move assignment operator). The problematic line is:

    // Required so that assert(m_check_invariants()); works.                                                                            
    assert((b.m_bits = buffer_type()).empty());                                     

Since construction of buffer_type requires an allocator argument. This patch simply passes get_allocator() to construct it.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.55%. Comparing base (d4be7a4) to head (2e28eb2).
Report is 20 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop      #84      +/-   ##
===========================================
- Coverage    95.80%   95.55%   -0.26%     
===========================================
  Files            5        5              
  Lines          668      675       +7     
  Branches         0      210     +210     
===========================================
+ Hits           640      645       +5     
- Misses          28       29       +1     
- Partials         0        1       +1     

Files with missing lines	Coverage Δ
include/boost/dynamic_bitset/dynamic_bitset.hpp	95.21% <100.00%> (-0.28%)	⬇️

... and 1 file with indirect coverage changes

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