On the svn-auth-x509 branch: Revert all encoding conversion API
changes made on this branch.

* subversion/include/svn_utf.h
  (svn_utf_string_to_utf8_ex): Remove prototype.
* subversion/libsvn_subr/utf.c
  (convert_string, svn_utf_string_to_utf8_ex): Remove.
  (svn_utf_string_to_utf8): Revert to trunk implementation.
* subversion/libsvn_subr/win32_xlate.c: Revert to trunk.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/svn-auth-x509@1613627 13f79535-47bb-0310-9956-ffa450edef68