Fix PR c++/109958: ICE taking the address of bound static member function brought...

Fix PR c++/109958: ICE taking the address of bound static member function brought into derived class by using-declaration

We currently ICE upon the following because we don't properly handle the
overload created for B::f through the using statement.

=== cut here ===
struct B { static int f(); };
struct D : B { using B::f; };
void f(D d) { &d.f; }
=== cut here ===

This patch makes build_class_member_access_expr and cp_build_addr_expr_1 handle
such overloads, and fixes the PR.

Successfully tested on x86_64-pc-linux-gnu.

	PR c++/109958

gcc/cp/ChangeLog:

	* typeck.cc (build_class_member_access_expr): Handle single OVERLOADs.
	(cp_build_addr_expr_1): Likewise.

gcc/testsuite/ChangeLog:

	* g++.dg/overload/using6.C: New test.