Provide initial regress for lhash.

For now, this is very limited and only tests calling lh_doall_arg()
multiple times on an empty linked hash. This process currently triggers
a SIGSEGV, which will be soon fixed.

regress/lib/libcrypto/lhash/Makefile

@@ -0,0 +1,12 @@
+#	$OpenBSD: Makefile,v 1.1 2024/05/06 14:31:25 jsing Exp $
+
+PROG =	lhash_test
+
+DPADD+=		${LIBCRYPTO}
+WARNINGS=	Yes
+LDFLAGS+=	-lcrypto
+CFLAGS+=	-DLIBRESSL_INTERNAL
+CFLAGS+=	-Wall -Wundef -Werror
+CFLAGS+=	-I${.CURDIR}/../../../../lib/libcrypto
+
+.include <bsd.regress.mk>

regress/lib/libcrypto/lhash/lhash_test.c

@@ -0,0 +1,59 @@
+/*	$OpenBSD: lhash_test.c,v 1.1 2024/05/06 14:31:25 jsing Exp $	*/
+/*
+ * Copyright (c) 2024 Joel Sing <jsing@openbsd.org>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <openssl/lhash.h>
+
+static void
+test_doall_fn(void *arg1, void *arg2)
+{
+}
+
+static int
+test_lhash_doall(void)
+{
+	_LHASH *lh;
+	int i;
+	int failed = 1;
+
+	if ((lh = lh_new(NULL, NULL)) == NULL)
+		goto failure;
+
+	/* Call doall multiple times while linked hash is empty. */
+	for (i = 0; i < 100; i++)
+		lh_doall_arg(lh, test_doall_fn, NULL);
+
+	lh_free(lh);
+
+	failed = 0;
+
+ failure:
+	return failed;
+}
+
+int
+main(int argc, char **argv)
+{
+	int failed = 0;
+
+	failed |= test_lhash_doall();
+
+	return failed;
+}