Don't promote asynch EH invokes of nounwind functions to calls

Don't promote asynch EH invokes of nounwind functions to calls

If the landingpad of the invoke is using a personality function that
catches asynch exceptions, then it can catch a trap.

Also add some landingpads to invalid LLVM IR test cases that lack them.

Over-the-shoulder reviewed by David Majnemer.

llvm-svn: 228782