PrettyPatch should handle "delta" patch mechanism in git binary patches

PrettyPatch should handle "delta" patch mechanism in git binary patches
https://bugs.webkit.org/show_bug.cgi?id=67628

Git patches are encoded using two mechanisms - "literal" and "delta".
See this email from the git mailing list archive for info
http://marc.info/?l=git&m=114682417113315&w=2

When determining if a binary file patch is an image or not we should accept
both literal and delta patch encodings.

Patch by Ben Wells <benwells@chromium.org> on 2011-09-06
Reviewed by Shinichiro Hamaji.

* PrettyPatch/PrettyPatch.rb:
* PrettyPatch/PrettyPatch_test.rb:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@94554 268f45cc-cd09-0410-ab3c-d52691b4dbfc