Add multi-threading to svnserve.  Whether threads are used is a run-time decision.  Platforms with threads but not fork (Windows) will use threads by default, platforms with both threads and fork (Unix) will use fork by default.
Add multi-threading to svnserve.  Whether threads are used is a
run-time decision.  Platforms with threads but not fork (Windows)
will use threads by default, platforms with both threads and fork
(Unix) will use fork by default.

* subversion/svnserve/main.c
  (enum connection_handling_mode, struct serve_thread_t, serve_thread): New.
  (main): Add multi-thread mode.  Add -F/-T/-S options to select fork,
  multi-thread or single-thread mode.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@846184 13f79535-47bb-0310-9956-ffa450edef68

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