Add the following Clang plugins:

PrintNamesAndSizes
  -Find top-level type definitions.  Print their kind (struct, enum, etc), typename, size, and location.
FindAffectedInterfaces
  -Given some typenames, find other types which are affected if that type changes.  This is specifically for determining which interfaces are affected by changing a struct or structs.

Also add a Makefile to build the plugins and a README describing how to run them.

Also add a python script that runs PrintNamesAndSizes with several different targets and generates compile-time checks in to the PPAPI source code to enforce that sizes are consistent, or if they change, we find out quickly.

This was broken off from a bigger CL:
http://codereview.chromium.org/5340003/
BUG=61004,92983
TEST=None

See this CL for an example of what these plugins helped me do:
http://codereview.chromium.org/5674004


Review URL: http://codereview.chromium.org/5730003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@69187 0039d316-1c4b-4281-b951-d872f2087c98