[CodeGen][ObjC] Emit invoke instead of call to call `objc_release` when

necessary.

Prior to r349952, clang used to call objc_msgSend when sending a release
messages, emitting an invoke instruction instead of a call instruction
when it was necessary to catch an exception. That changed in r349952
because runtime function objc_release is called as a nounwind function,
which broke programs that were overriding the dealloc method and
throwing an exception from it. This patch restores the behavior prior to
r349952.

rdar://problem/50253394

Differential Revision: https://reviews.llvm.org/D61803

llvm-svn: 360474