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

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@211702 91177308-0d34-0410-b5e6-96231b3b80d8
Apparently, some versions of diff like -U0 more than -u0.


git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@211703 91177308-0d34-0410-b5e6-96231b3b80d8
Rolling back, as the test fails on one of the buildbots:
  http://lab.llvm.org:8011/builders/clang-hexagon-elf/builds/13505/steps/check-all/logs/Clang%20Tools%3A%3Ac-style-casts.cpp



git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@211708 91177308-0d34-0410-b5e6-96231b3b80d8