Improve the speed of the xdelta algorithm by avoiding lots of small memory copying.
Improve the speed of the xdelta algorithm by avoiding lots of small memory
copying.

Review by: jerenkrantz
           julianfoad

* subversion/libsvn_delta/xdelta.c (find_match): Take a pointer to the
  length of the pending insert instead of a stringbuf.
  (compute_delta): Keep track of the start and length of the new data that is
  pending to insert instead of stuffing the new data (one byte at a time:-)
  in a stringbuf.  Remove useless assert (for readability).

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion