ftpd: replace malloc + memset 0 with calloc.

It is faster and usually safer.
Use NULL instead of zero for the pointer.

libexec/ftpd/popen.c

@@ -81,9 +81,8 @@ ftpd_popen(char *program, char *type)
 	if (!pids) {
 		if ((fds = getdtablesize()) <= 0)
 			return (NULL);
-		if ((pids = malloc(fds * sizeof(int))) == NULL)
+		if ((pids = calloc(fds, sizeof(int))) == NULL)
 			return (NULL);
-		memset(pids, 0, fds * sizeof(int));
 	}
 	if (pipe(pdes) < 0)
 		return (NULL);
@@ -185,7 +184,7 @@ ftpd_pclose(FILE *iop)
 	 * pclose returns -1 if stream is not associated with a
 	 * `popened' command, or, if already `pclosed'.
 	 */
-	if (pids == 0 || pids[fdes = fileno(iop)] == 0)
+	if (pids == NULL || pids[fdes = fileno(iop)] == 0)
 		return (-1);
 	(void)fclose(iop);
 	omask = sigblock(sigmask(SIGINT)|sigmask(SIGQUIT)|sigmask(SIGHUP));