The result of the Microsoft __uuidof operator must be considered a global...

The result of the Microsoft __uuidof operator must be considered a global lvalue during constant expression evaluation.
Otherwise we would get this error in C++11 mode (because of a recent change):
   error: non-type template argument of type 'const _GUID *' is not a constant expression

For code like:
template <const GUID* g = &__uuidof(struct_with_uuid)>
class COM_CLASS { };

llvm-svn: 154790