New Test-Case for Region Analysis

While working on improvements to the region info analysis, this test case caused
an incorrect region 1 => 2 to be detected.  It is incorrect because entry has an
outgoing edge to 3.  This is interesting because 1 dom 2 and 2 pdom 1, which
should have been enough to prevent incoming forward edges into the region and
outgoing forward edges from the region.

Reviewers: grosser

Subscribers: llvm-commits

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

Differential Revision: https://reviews.llvm.org/D30603

llvm-svn: 296988