Remove unnecessary LAMBDA_EXPR fields.

Remove unnecessary LAMBDA_EXPR fields.

	* cp-tree.h (LAMBDA_EXPR_CLOSURE): Use TREE_TYPE.
	(LAMBDA_EXPR_RETURN_TYPE): Remove.
	(struct tree_lambda_expr): Remove closure and return_type fields.
	* lambda.c (build_lambda_expr): Don't set LAMBDA_EXPR_RETURN_TYPE.
	* pt.c (tsubst_copy_and_build): Likewise.
	* parser.c (cp_parser_lambda_declarator_opt): Track return type.
	(cp_parser_lambda_body): Adjust unspecified return type check.
	* ptree.c (cxx_print_lambda_node): Don't print closure or
	return type.

From-SVN: r251430