Fix fragile-ABI ObjC exceptions in the presence of optimization with

Fix fragile-ABI ObjC exceptions in the presence of optimization with
the magic of inline assembly.  Essentially we use read and write hazards
on the set of local variables to force flushing locals to memory
immediately before any protected calls and to inhibit optimizing locals
across the setjmp->catch edge.  Fixes rdar://problem/8160285

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@109960 91177308-0d34-0410-b5e6-96231b3b80d8