Mojo C++ bindings

This CL includes code for a static library that supports C++ bindings to the Mojo message format. A sample interface with "generated" bindings is included in the sample/ folder along with sample_test.cc that shows how the generated code may be used.

This is a WIP but seems worth snapshotting as is. See the TODO file for a list of near term improvements, most notably testing.

Originally reviewed at https://codereview.chromium.org/23913008/
Then subsequently at https://codereview.chromium.org/27034003/

TBR=grt@chromium.org

Review URL: https://codereview.chromium.org/27064002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@228240 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 228240