Make verify-po.py optionally use msgfmt to check the syntax of po files.
Make verify-po.py optionally use msgfmt to check the syntax of po files.

* tools/hook-scripts/verify-po.py
  (USE_MSGFMT): Conditional to enable msgfmt checking.
  (MsgFmtChecker): New class to run msgfmt via a pipe.
  (ChangeReceiver.close_file): Run po files thought MsgFmtChecker.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@851241 13f79535-47bb-0310-9956-ffa450edef68

wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,wbond/subversion,wbond/subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion,YueLinHo/Subversion,wbond/subversion