Followup to r18363.  Correct some confusion and typos in a doc-comment.
Followup to r18363.  Correct some confusion and typos in a doc-comment.

* subversion/libsvn_delta/svndiff.c
  (zlib_encode): Correctly state the boundary conditions for compression,
    correct a typo, and restate the behaviour of this function in the
    event that the input does not compress (based on the assumptions
    documented in zlib_decode()).


git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@858440 13f79535-47bb-0310-9956-ffa450edef68

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