Extract common code.

* subversion/libsvn_ra_serf/update.c
  (process_buffer): New helper for update_delay_handler() and 
   process_pending(). Extracted from update_delay_handler().
  (update_delay_handler, process_pending): Use process_buffer().


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1558843 13f79535-47bb-0310-9956-ffa450edef68