Sema: handle additional case of qualified types

A second instance of attributed types escaped the previous change, identified
thanks to Richard Smith!  When deducing the void case, we would also assume that
the type would not be attributed.  Furthermore, properly handle multiple
attributes being applied to a single TypeLoc.

Properly handle this case and future-proof a bit by ignoring parenthesis
further.  The test cases do use the additional parenthesis to ensure that this
case remains properly handled.

Addresses post-commit review comments from Richard Smith to SVN r219851.

llvm-svn: 219974