c++: local-decls are never member fns [PR97186]

c++: local-decls are never member fns [PR97186]

This fixes an ICE in noexcept instantiation.  It was presuming
functions always have template_info, but that changed with my
DECL_LOCAL_DECL_P changes.  Fortunately DECL_LOCAL_DECL_P fns are
never member fns, so we don't need to go fishing out a this pointer.

Also I realized I'd misnamed local10.C, so renaming it local-fn3.C,
and while there adding the effective-target lto that David E pointed
out was missing.

	PR c++/97186
	gcc/cp/
	* pt.c (maybe_instantiate_noexcept): Local externs are never
	member fns.
	gcc/testsuite/
	* g++.dg/template/local10.C: Rename ...
	* g++.dg/template/local-fn3.C: .. here.  Require lto.
	* g++.dg/template/local-fn4.C: New.