roken: qsort provide ANSI C prototype for swapfunc()

K&R is no longer acceptable.

lib/roken/qsort.c

@@ -69,9 +69,7 @@ static inline void	 swapfunc(char *, char *, int, int);
 	es % sizeof(long) ? 2 : es == sizeof(long)? 0 : 1;
 
 static inline void
-swapfunc(a, b, n, swaptype)
-	char *a, *b;
-	int n, swaptype;
+swapfunc(char *a, char *b, int n, int swaptype)
 {
 	if(swaptype <= 1)
 		swapcode(long, a, b, n)