Revision 1683895

Simplify code and avoid multiple buffer reallocation for every delta
window in SVNDIFF stream processing.

* subversion/libsvn_delta/svndiff.c
  (write_handler): Use svn_stringbuf_remove() to remove processed 
   window data from buffer. Clear subpool on every window procesing 
   instead of creating new subpool and destroy old one.
  (svn_txdelta_parse_svndiff): Allocate DB->BUFFER in DB->POOL instead of
   DB->SUBPOOL.