Clang16 will not allow implicit function declarations and implicit integers etc.
This patch overhauls the source code for modern C.

Bug: https://bugs.gentoo.org/875029

Signed-off-by: Pascal Jäger <pascal.jaeger@leimstift.de>

--- a/strnstr.c
+++ b/strnstr.c
@@ -46,10 +46,7 @@ static char sccsid[] = "@(#)strstr.c	8.1 (Berkeley) 6/4/93";
  * first slen characters of s.
  */
 char *
-strnstr(s, find, slen)
-	const char *s;
-	const char *find;
-	size_t slen;
+strnstr(const char *s, const char *find, size_t slen)
 {
 	char c, sc;
 	size_t len;