For issue #3747, 'svn patch' support of svn:mergeinfo, make it
possible to parse svn:mergeinfo diffs regardless of i18n.

* subversion/libsvn_diff/util.c
  (display_mergeinfo_diff): Print a hunk header line for mergeinfo diffs.
   The header indicates the number of reverse-merges and forward-merges in
   the diff. Before this change, this information was only printed as part
   of output which is translated for i18n. This made it impossible to reliably
   parse svn:mergeinfo diffs from patch files.
   Futher changes to the diff parser and svn patch are coming soon.

* subversion/tests/cmdline/merge_tests.py
  (merge_in_new_file_and_diff): Adjust expected output.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1598092 13f79535-47bb-0310-9956-ffa450edef68