c++: xobj lambda 'this' capture [PR113563]

c++: xobj lambda 'this' capture [PR113563]

Various places were still making assumptions that we could get to the 'this'
capture through current_class_ref in a lambda op(), which is incorrect for
an explicit object op().

	PR c++/113563

gcc/cp/ChangeLog:

	* lambda.cc (build_capture_proxy): Check pointerness of the
	member, not the proxy type.
	(lambda_expr_this_capture): Don't assume current_class_ref.
	(nonlambda_method_basetype): Likewise.
	* semantics.cc (finish_non_static_data_member): Don't assume
	TREE_TYPE (object) is set.
	(finish_this_expr): Check current_class_type for lambda,
	not current_class_ref.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp23/explicit-obj-lambda16.C: New test.