PR c++/79092 - non-type args of different types are different

PR c++/79092 - non-type args of different types are different

	* tree.c (cp_tree_equal): Check the type of constants.
	* pt.c (unify) [TEMPLATE_PARM_INDEX]: Handle UNIFY_ALLOW_INTEGER
	when comparing to previously deduced argument.
	(maybe_convert_nontype_argument): New.
	(convert_nontype_argument): Call it.
	(tsubst_copy_and_build): Handle partial instantiation of
	IMPLICIT_CONV_EXPR.
	(unify): Ignore type when deducing from array bound.
	(dependent_type_p_r): Handle DEFERRED_NOEXCEPT.
	(value_dependent_expression_p): Any type-dependent expression is
	value-dependent.  Handle IMPLICIT_CONV_EXPR.
	* cp-tree.h (IMPLICIT_CONV_EXPR_NONTYPE_ARG): New.
	* mangle.c (write_template_arg): Strip IMPLICIT_CONV_EXPR.

From-SVN: r254843