Teach the file merge code to recognize keyword translation even in 'binary'
files.  Fixes issue #4221 "Trivial merge of a binary file with svn:keywords
raises a conflict".  The problem was that in deciding whether a trivial
merge is possible, it wasn't detranslating keywords in the working file
before comparing with the incoming left and right files.

* subversion/libsvn_wc/merge.c
  (detranslate_wc_file): Detranslate keywords even in 'binary' files.

* subversion/tests/cmdline/merge_tests.py
  (merge_binary_file_with_keywords): Extend to test multiple permutations.


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1435195 13f79535-47bb-0310-9956-ffa450edef68