[WinEH] Recognize CoreCLR personality function

Summary:
 - Add CoreCLR to if/else ladders and switches as appropriate.
 - Rename isMSVCEHPersonality to isFuncletEHPersonality to better
   reflect what it captures.

Reviewers: majnemer, andrew.w.kaylor, rnk

Subscribers: pgavlin, AndyAyers, llvm-commits

Differential Revision: http://reviews.llvm.org/D13449

llvm-svn: 249455