In Parser::isCXXDeclarationSpecifier, consider a non-type identifier

In Parser::isCXXDeclarationSpecifier, consider a non-type identifier
followed by an identifier as declaration specificer (except for ObjC).
This allows e.g. an out-of-line C++ member function definitions to be
recognized as functions and not as variable declarations if the type
name for the first parameter is not recognized as a type--say, when there
is a function name shadowing an enum type name and the parameter is
missing the "enum" keyword needed to distinguish the two.

Note that returning TPResult::Error() instead of TPResult::True()
appears to have the same end result, while TPResult::Ambiguous()
results in a crash.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@155163 91177308-0d34-0410-b5e6-96231b3b80d8