[clang-tidy] Extend TransformerClangTidyCheck to support adding includes.

Summary:
This revision implements support for the `AddedIncludes` field in
RewriteRule cases; that is, it supports specifying the addition of include
directives in files modified by the clang tidy check.

Reviewers: ilya-biryukov, gribozavr

Subscribers: xazax.hun, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D63893

llvm-svn: 364922