c++/modules: befriending template from current class scope

c++/modules: befriending template from current class scope

Here the TEMPLATE_DECL representing the template friend declaration
naming B has class scope since the template B has class scope, but
get_merge_kind assumes all DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P
TEMPLATE_DECL have namespace scope and wrongly returns MK_named instead
of MK_local_friend for the friend.

gcc/cp/ChangeLog:

	* module.cc (trees_out::get_merge_kind) <case depset::EK_DECL>:
	Accomodate class-scope DECL_UNINSTANTIATED_TEMPLATE_FRIEND_P
	TEMPLATE_DECL.  Consolidate IDENTIFIER_ANON_P cases.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/friend-7.h: New test.
	* g++.dg/modules/friend-7_a.H: New test.
	* g++.dg/modules/friend-7_b.C: New test.

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