Add verifyAnalysis for LCSSA.

Summary:
LCSSAWrapperPass currently doesn't override verifyAnalysis method, so pass
manager doesn't verify LCSSA. This patch adds the method so that we start
verifying LCSSA between loop passes.

Reviewers: chandlerc, sanjoy, hfinkel

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D22888

llvm-svn: 276941