There are times when the landing pad won't have a call to 'eh.selector' in

There are times when the landing pad won't have a call to 'eh.selector' in
it. It's been assumed up til now that it would be in its immediate
successor. However, this isn't necessarily the case. It could be in one of its
successor's successors.

Modify the code to more thoroughly check for an 'eh.selector' call in
successors. It only looks at a successor if we get there as a result of an
unconditional branch.

Testcase ObjC/exceptions-4.m in r126968.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@126969 91177308-0d34-0410-b5e6-96231b3b80d8