c++: mem-initializer-id qualified name lookup is type-only [PR122192]

c++: mem-initializer-id qualified name lookup is type-only [PR122192]

Since a mem-initializer needs to be able to initialize any base class,
lookup for which is type-only, we in turn need to make mem-initializer-id
qualified name lookup type-only too.

	PR c++/122192

gcc/cp/ChangeLog:

	* parser.cc (cp_parser_mem_initializer_id): Pass class_type
	instead of typename_type to cp_parser_class_name in the
	nested-name-specifier case.

gcc/testsuite/ChangeLog:

	* g++.dg/template/dependent-base6.C: Verify mem-initializer-id
	qualified name lookup is type-only too.

Reported-by: Vincent X
Reviewed-by: Jason Merrill <jason@redhat.com>