c++: Fix constexpr ICE from const mismatch [PR91607]

gcc/cp/ChangeLog
2020-03-04  Jason Merrill  <jason@redhat.com>

	PR c++/91607
	* constexpr.c (constexpr_call_hasher::equal): Use
	same_type_ignoring_top_level_qualifiers_p.
2 files changed