Added an inserter for ArrayRef<SourceRange>.

Summary:
Added an inserter for ArrayRef<SourceRange>, as it is already needed in at least
two places (static analyzer and clang-tidy).

Reviewers: jordan_rose

CC: cfe-commits, gribozavr

Differential Revision: http://llvm-reviews.chandlerc.com/D2984

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203117 91177308-0d34-0410-b5e6-96231b3b80d8