[GlobalMerge] Handle non-landingpad EH pads

This code crashed on funclet-style EH instructions such as catchpad,
catchswitch, and cleanuppad. Just treat all EH pad instructions
equivalently and avoid merging the globals they reference through any
use.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@284633 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed