Minor optimization in diff code: stop comparing data once we found a mismatch.
Further iterations won't change the result.

* subversion/libsvn_diff/diff_file.c
  (find_identical_suffix): exit the loops as soon as CAN_READ_WORD or IS_MATCH
                           are FALSE

git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1485488 13f79535-47bb-0310-9956-ffa450edef68