XDelta calculation is major part of svn_txdelta_send_txstream. Therefore, speed up string matching code and the relatively expensive hash-code (adler32) calculations.
XDelta calculation is major part of svn_txdelta_send_txstream.
Therefore, speed up string matching code and the relatively
expensive hash-code (adler32) calculations.

* subversion/libsvn_delta/xdelta.c
  (init_adler32): init adler checksum with 0 instead of 1;
   use svn_adler32 for performance
  (adler32_out): "-1" can / must be ommitted now that we
   start at 0 instead of 1 for s1.
  (adler32_replace): special, faster implementation replacing
   a adler32_out(), adler32_in() sequence

  (match_length): new utility function
  (find_match): speed up the main loop by calling match_length()
  (compute_delta): optimize adler32 calculations

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1054286 13f79535-47bb-0310-9956-ffa450edef68

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