re PR c++/67810 (Non-expression recognized as fold expression)

re PR c++/67810 (Non-expression recognized as fold expression)

	PR c++/67810
	* parser.c (cp_parser_fold_expr_p): Remove.
	(is_binary_op): New.
	(cp_parser_fold_expression): Take LHS as parameter.
	(cp_parser_primary_expression): Call it after parsing an expression.
	(cp_parser_binary_expression, cp_parser_assignment_operator_opt)
	(cp_parser_expression): Ignore an operator followed by '...'.
	(is_binary_op): New.
	* pt.c (tsubst_unary_left_fold, tsubst_binary_left_fold)
	(tsubst_unary_right_fold, tsubst_binary_right_fold): Handle errors.

From-SVN: r228556