Add the usual header controls.  No functional change.
Add the usual header controls.  No functional change.

* subversion/include/private/svn_packed_data.h
  (): add #include blocker and extern "C" definition

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1509928 13f79535-47bb-0310-9956-ffa450edef68

YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion,YueLinHo/Subversion