In the Win32 resource compiler: stop including APR and several system headers
just to produce a nice version string. This slows down compilation and
generates several warnings per compiled library. (Too long macros, etc.)

* build/win32/svn.rc
  (SVN_WIN32_RESOURCE_COMPILATION): New explicit define.
  (APR_STRINGIFY): Define locally.

* subversion/include/svn_version.h
  (#ifdef SVN_WIN32_RESOURCE_COMPILATION): Use this check to skip including
    all headers instead of just ignoring once based on an APR define.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1532287 13f79535-47bb-0310-9956-ffa450edef68