Create modernize-make-unique check.

Summary: create a check that replaces 'std::unique_ptr<type>(new type(args...))' with 'std::make_unique<type>(args...)'. It was on the list of "Ideas for new Tools". It needs to be tested more carefully, but first I wanted to know if you think it is worth the effort.

Reviewers: klimek

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D13166

llvm-svn: 248785