protocol-qualifier list without a leading type (e.g., <#blah#>), don't
complain about it being an archaic protocol-qualifier list unless it
actually parses as one.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@119805 91177308-0d34-0410-b5e6-96231b3b80d8
Douglas Gregor