[arcmt] Before applying '__weak' check whether the objc class is annotated with objc_arc_weak_reference_unavailable
or is in a list of classes not supporting 'weak'.

rdar://9489367.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@135002 91177308-0d34-0410-b5e6-96231b3b80d8
6 files changed