* typeck2.c (store_init_value): Always call
	require_potential_constant_expression.
	* pt.c (convert_nontype_argument): Likewise.
	* constexpr.c (potential_constant_expression_1): Adjust message.
	Use decl_maybe_constant_var_p instead of decl_constant_var_p.
	* decl2.c (decl_maybe_constant_var_p): Consider initializer.

From-SVN: r249382