Add a check to flag the usage of C-style casts (Google Style).

Summary:
Add a check to flag the usage of C-style casts, as per Google Style
Guide:
http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml?showone=Casting#Casting

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4189