re PR c++/50800 (Internal compiler error in finish_member_declarations, possibly related to may_alias attribute)

	PR c++/50800
gcc/
	* tree.c (build_reference_type_for_mode): Don't pass can_alias_all
	down when building TYPE_CANONICAL.
	(build_pointer_type_for_mode): Likewise.
gcc/cp/
	* typeck.c (structural_comptypes): Don't check TYPE_REF_CAN_ALIAS_ALL.

From-SVN: r222419