Mark svn-rep-sharing-stats as experimental.
Mark svn-rep-sharing-stats as experimental.

* tools/server-side/svn-rep-sharing-stats.c
  (check_experimental):
    New.  Errors out unless an environment variable is set.
  (main):
    Call check_experimental().

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@880046 13f79535-47bb-0310-9956-ffa450edef68

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