c++: Don't ICE to build private access error message [PR116323]

c++: Don't ICE to build private access error message [PR116323]

We currently ICE upon the following code while building the "[...] is
private within this context" error message

=== cut here ===
class A { enum Enum{}; };
template<typename E, template<typename> class Alloc>
class B : private Alloc<E>, private A {};
template<typename E, template<typename> class Alloc>
int B<E, Alloc>::foo (Enum m) { return 42; }
=== cut here ===

The problem is that since r11-6880, after detecting that Enum cannot be
accessed in B, enforce_access will access the TYPE_BINFO of all the
bases of B, which ICEs for any that is a BOUND_TEMPLATE_TEMPLATE_PARM.
This patch simply skips such bases.

	PR c++/116323

gcc/cp/ChangeLog:

	* search.cc (get_parent_with_private_access): Only call access_in_type
	for RECORD_OR_UNION_TYPE_P base BINFOs.

gcc/testsuite/ChangeLog:

	* g++.dg/template/access43.C: New test.