[WinEH] Update CoreCLR EH for catchpad MBBs

Summary:
Set the pad MBB as a funclet entry for CoreCLR as well as MSVCCXX, and
update state numbering to put the catchpad block rather than its normal
successor into the unwind map.

Reviewers: majnemer

Subscribers: llvm-commits

Differential Revision: http://reviews.llvm.org/D13492

llvm-svn: 249569