Add documentation for -Rpass*

Summary:
This adds documentation for -Rpass, -Rpass-missed and -Rpass-analysis.
It also adds release notes for 3.5.

Reviewers: rsmith

Subscribers: cfe-commits

Differential Revision: http://reviews.llvm.org/D3730

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@209841 91177308-0d34-0410-b5e6-96231b3b80d8