On the log-message-templates branch, add a test for the
svn_client_get_log_message_templates() API.

* subversion/tests/libsvn_client/client-test.c
  (test_log_message_templates, test_funcs): New test.


git-svn-id: https://svn.apache.org/repos/asf/subversion/branches/log-message-templates@1623967 13f79535-47bb-0310-9956-ffa450edef68