[WinEH] Make FuncletLayout more robust against catchret

[WinEH] Make FuncletLayout more robust against catchret

Catchret transfers control from a catch funclet to an earlier funclet.
However, it is not completely clear which funclet the catchret target is
part of.  Make this clear by stapling the catchret target's funclet
membership onto the CATCHRET SDAG node.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@249052 91177308-0d34-0410-b5e6-96231b3b80d8