c++: Non-inline temploid friends should still be COMDAT [PR122819]

c++: Non-inline temploid friends should still be COMDAT [PR122819]

Modules allow temploid friends to no longer be implicitly inline, as
functions defined in a class body will not be implicitly inline if
attached to a named module.

This requires us to clean up linkage handling a little bit, mostly by
replacing usages of 'DECL_TEMPLATE_INSTANTIATION' with
'DECL_TEMPLOID_INSTANTIATION' when determining if an entity has vague
linkage.

	PR c++/122819

gcc/cp/ChangeLog:

	* decl.cc (start_preparsed_function): Use
	DECL_TEMPLOID_INSTANTIATION instead of
	DECL_TEMPLATE_INSTANTIATION to check vague linkage.
	* decl2.cc (vague_linkage_p): Likewise.
	(c_parse_final_cleanups): Simplify condition.
	* semantics.cc (expand_or_defer_fn_1): Also check for temploid
	friend functions.

gcc/testsuite/ChangeLog:

	* g++.dg/modules/tpl-friend-22.C: New test.

Signed-off-by: Nathaniel Shead <nathanieloshead@gmail.com>
Reviewed-by: Jason Merrill <jason@redhat.com>