BACKPORT: Support 'Language' header field of PO files (#76)

[sils]

GNU gettext has support for the 'Language' field in header entry since
version 0.18 (May 2010). This commit adds support for the field and
addresses #76.

[codecov-io]

Current coverage is 82.56%

Merging #225 into 2.x-maintenance will increase coverage by +0.01% as of ccc12a7

@@            2.x-maintenance    #225   diff @@
===============================================
  Files                    21      21       
  Stmts                  3709    3711     +2
  Branches                  0       0       
  Methods                   0       0       
===============================================
+ Hit                    3062    3064     +2
  Partial                   0       0       
  Missed                  647     647       

Review entire Coverage Diff as of ccc12a7

Powered by Codecov. Updated on successful CI builds.

[sils]

@rultor merge please

[rultor]

@rultor merge please

@sils1297 OK, I'll try to merge now. You can check the progress of the merge here

[rultor]

@rultor merge please

@sils1297 Oops, I failed. You can see the full log here (spent 10s)

+ echo -e 'Host github.com\n\tStrictHostKeyChecking no\n'
+ chmod 600 /home/rultor/.ssh/config
+ git clone [email protected]:python-babel/babel.git repo
Cloning into 'repo'...
+ cd repo
+ git config user.email [email protected]
+ git config user.name rultor
+ '[' -z 'echo "Nothing to do (yet)."' ']'
+ cd ..
+ cat
+ '[' false = true ']'
+ cat
+ chmod a+x entry.sh
+ cat
+ echo 'echo "Nothing to do (yet)."' ';'
+ rm -rf .gpg
+ cd repo
+ git remote add fork [email protected]:sils1297/babel.git
+ git remote update
Fetching origin
Fetching fork
From github.com:sils1297/babel
 * [new branch]      1.x-maintenance -> fork/1.x-maintenance
 * [new branch]      2.x-maintenance -> fork/2.x-maintenance
 * [new branch]      feature/cldr24 -> fork/feature/cldr24
 * [new branch]      master     -> fork/master
 * [new branch]      patch-1    -> fork/patch-1
 * [new branch]      sils/ci    -> fork/sils/ci
 * [new branch]      sils/coverage -> fork/sils/coverage
 * [new branch]      sils/linear -> fork/sils/linear
 * [new branch]      sils/maint -> fork/sils/maint
 * [new branch]      sils/py35  -> fork/sils/py35
 * [new branch]      sils/testpr -> fork/sils/testpr
+ args=
+ '[' default == default ']'
+ args=' --ff'
+ '[' default == no ']'
+ '[' default == only ']'
+ export BRANCH=__rultor
+ BRANCH=__rultor
++ git show-branch __rultor
+ '[' 0 -gt 0 ']'
+ git checkout fork/2.x-maintenance
Note: checking out 'fork/2.x-maintenance'.

You are in 'detached HEAD' state. You can look around, make experimental
changes and commit them, and you can discard any commits you make in this
state without impacting any branches by performing another checkout.

If you want to create a new branch to retain commits you create, you may
do so (now or later) by using -b with the checkout command again. Example:

  git checkout -b new_branch_name

HEAD is now at 470f6aa... Support 'Language' header field of PO files (#76)
+ git checkout -b __rultor
Switched to a new branch '__rultor'
+ git checkout 2.x-maintenance
error: pathspec '2.x-maintenance' did not match any file(s) known to git.

[sils]

merging backport without additional approval as commit was already acknowledged.