Patch to resolve shared library multiple definition conflicts.

    # Patch to deal with protobuf problems in MacOsX
    # Details  : https://bitbucket.org/osrf/release-tools/issue/25
    # Upstream : http://code.google.com/p/protobuf/issues/detail?id=128

patch courtesy of @j-rivero
https://github.com/j-rivero/homebrew-protobuf