[RegionInfo] Verify getRegionFor

Summary:
Check the contents of BBtoRegion during analysis verification. It only takes place if -verify-region-info is passed or LLVM is compiled with XDEBUG.

RegionBase<Tr>::verifyRegion() also checks the RegionInfoBase<Tr>::VerifyRegionInfo flag, which is redundant, but verifyRegion() is public API and might be invoked from other sites. In order to avoid behavioral change, this check is not removed. In any case, no region will be verified unless VerifyRegionInfo is set.

Reviewers: grosser

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D11872

llvm-svn: 244611