c++: check alias match for specializations [PR98116]

c++: check alias match for specializations [PR98116]

This fixes the underlying problem my recent (backedout) changes to
array type creation uncovered.  We had paths through
structural_comptypes that ignored alias templates, even when
significant.  This adds the necessary checks.

	PR c++/98116
	gcc/cp/
	* typeck.c (structural_comptypes): Move early outs to comptype.
	Always check template-alias match when comparing_specializations.
	(comptypes): Do early out checking here.
	gcc/testsuite/
	* g++.dg/template/pr98116.C: Remove dg-ice.
	* g++.dg/template/pr98116-2.C: New.