tests/lint: add tests for C90 mode and malformed declarations

In the grammar, 148 lines are still uncovered by the tests.  The
untested parts are mostly obscure declarations and a few parse errors.


(rillig)

/*	$NetBSD: msg_000_c90.c,v 1.1 2021/07/08 05:18:49 rillig Exp $	*/
# 3 "msg_000_c90.c"

/*
 * Test for message: empty declaration [0]
 *
 * In strict C90 mode, an empty declaration is an error, not merely a warning.
 */

/* lint1-flags: -s */

/* expect+1: error: empty declaration [0] */
;

msg_000_c90.c(13): error: empty declaration [0]

/*	$NetBSD: msg_001_c90.c,v 1.1 2021/07/08 05:18:49 rillig Exp $	*/
# 3 "msg_001_c90.c"

/*
 * Test for message: old style declaration; add 'int' [1]
 *
 * In strict C90 mode, an old-style declaration is an error, not merely a
 * warning.
 */

/* lint1-flags: -s */

/* expect+1: error: old style declaration; add 'int' [1] */
implicit_global_variable;

msg_001_c90.c(14): error: old style declaration; add 'int' [1]

/*	$NetBSD: msg_272_c90.c,v 1.1 2021/07/08 05:18:49 rillig Exp $	*/
# 3 "msg_272_c90.c"

/*
 * Test for message: empty translation unit [272]
 *
 * In strict C90 mode, an empty translation unit is an error, not merely a
 * warning.
 */

/* lint1-flags: -s */

/* expect+1: error: empty translation unit [272] */

msg_272_c90.c(14): error: empty translation unit [272]