This patch does the following.

1) Issue digsnostics in non-fragile ABI, when an expression
   evaluates to an interface type (except when it is used to
   access a non-fragile ivar).
2) Issue unsupported error in fragile ABI when an expression
   evaluates to an interface type (except when it is used to
   access a fragile ivar).

llvm-svn: 80860