stylebot should warn when FeatureDefines differ
https://bugs.webkit.org/show_bug.cgi?id=125748

Reviewed by Dan Bernstein.

Add a stylebot checker that ensures that FeatureDefines.xcconfig files
are always exactly equal (and warns people adding new FeatureDefines.xcconfig files,
an unlikely occurrance, to add them to the list).

It's a bit nontraditional for stylebot because it will warn on existing errors in the tree,
but that is the most straightforward way to implement it (and we're at zero diffs right now).

* Scripts/webkitpy/style/checker.py:
(_all_categories):
(FileType):
(CheckerDispatcher._file_type):
(CheckerDispatcher._create_checker):
* Scripts/webkitpy/style/checkers/featuredefines.py: Added.
(FeatureDefinesChecker):
(FeatureDefinesChecker.__init__):
(FeatureDefinesChecker.check):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160611 268f45cc-cd09-0410-ab3c-d52691b4dbfc