Make the size of the thread pool in svnserve CL configurable.
Make the size of the thread pool in svnserve CL configurable.

* subversion/svnserve/svnserve.c
  (SVNSERVE_OPT_MIN_THREADS,
   SVNSERVE_OPT_MAX_THREADS): #define new option IDs
  (svnserve__options): Add option definitions if threads are available.
                       Unfortunately, there seems to be no way to use
                       THREADPOOL_*_SIZE constants here.
  (sub_main): Parse the new options and apply limits to the thread pool.

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1584353 13f79535-47bb-0310-9956-ffa450edef68

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