Mention the guarantees and non-guarantees associated with the path that will be returned by svn_fs_fs__path_rev_absolute().
Mention the guarantees and non-guarantees associated with the
path that will be returned by svn_fs_fs__path_rev_absolute().

* subversion/libsvn_fs_fs/fs_fs.c
  (svn_fs_fs__path_rev_absolute): improve commentary

git-svn-id: f8a4e5e023278da1e04e203c7fe051e3c4285d88@1042479 13f79535-47bb-0310-9956-ffa450edef68

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