New Test-Case for Region Analysis

While working on improvements to region info analysis, this test case caused an
incorrect region bb2 => bb3 to be detected.

Reviewers: grosser

Contributed-by: Nandini Singhal <cs15mtech01004@iith.ac.in>

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D30652

llvm-svn: 297014