Mark messages from our utf8proc wrapper as translatable.

* subversion/libsvn_subr/utf8proc.c
  (encode_ucs4, svn_utf__glob): Make messages translatable and more neutral.
  (svn_utf__glob): Fix escape-token length check.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1481619 13f79535-47bb-0310-9956-ffa450edef68
* subversion/tests/libsvn_subr/utf-test.c (test_utf_pattern_match):
   Add test case for empty custom escape token in LIKE mode.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1481620 13f79535-47bb-0310-9956-ffa450edef68