Refactor svndiff encoding code.
Refactor svndiff encoding code.

* subversion/libsvn_delta/svndiff.c
  (SVNDIFF_V0, SVNDIFF_V1, SVNDIFF_HEADER_SIZE): Move to top of the 
   file.
  (get_svndiff_header): New helper, returns SVNDIFF_V0 or SVNDIFF_V1
   depending of svndiff version requested.
  (send_simple_insertion_window, window_handler): Use 
   get_svndiff_header() helper and use SVNDIFF_HEADER_SIZE constant.


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1684054 13f79535-47bb-0310-9956-ffa450edef68

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