c++: Member fns and deduction guide rewriting [PR98929]

c++: Member fns and deduction guide rewriting [PR98929]

My patch for 96199 had us re-substitute the parameter types of a constructor
in order to rewrite mentions of members into dependent references.  We need
to do that for member functions, too.

gcc/cp/ChangeLog:

	PR c++/98929
	PR c++/96199
	* error.c (dump_expr): Ignore dummy object.
	* pt.c (tsubst_baselink): Handle dependent scope.

gcc/testsuite/ChangeLog:

	PR c++/98929
	* g++.dg/cpp1z/class-deduction-decltype1.C: New test.