Suggest automated replacements of C-style casts with C++ casts.

Summary:
This patch implements a subset of possible replacements of C-style
casts with const_cast/static_cast/reinterpret_cast. This should cover a large
portion of cases in real code. Handling of a few more cases may be implemented
eventually.

Reviewers: sbenza, djasper

Reviewed By: djasper

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D4478

llvm-svn: 212924