Add diff tool for IDL
Add diff tool for IDL

This CL adds a diff tool which will take all generated headers
found, and diff them against the matching original headers while
ignoring common difference that are not real issues such as 
blank lines, changes in whitespace, etc...

BUG= http://code.google.com/p/chromium/issues/detail?id=76271
TEST= python idl_diff.py --src=../c --gen=hdir


---Paths modified but not in any changelist:
Review URL: http://codereview.chromium.org/7242020

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@90609 0039d316-1c4b-4281-b951-d872f2087c98

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