Objective-C++ ARC: eliminate the utterly unjustified loophole that

silently dropped ownership qualifiers that were being applied to
ownership-qualified, substituted type that was *not* a substituted
template type parameter. We now provide a diagnostic in such cases,
and recover by dropping the added qualifiers.

Document this behavior in the ARC specification.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@133309 91177308-0d34-0410-b5e6-96231b3b80d8