Implemented formatting of rvalue references

Summary:
Handle "&&" usage as rvalue reference, added tests and fixed incorrect
tests that interfere with this feature.

http://llvm.org/bugs/show_bug.cgi?id=15051

Reviewers: djasper

Reviewed By: djasper

CC: cfe-commits, klimek

Differential Revision: http://llvm-reviews.chandlerc.com/D531

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@176874 91177308-0d34-0410-b5e6-96231b3b80d8