libbb: introduce and use xsettimeofday()

function                                             old     new   delta
xsettimeofday                                          -      25     +25
rdate_main                                           274     260     -14
step_time                                            348     331     -17
set_kernel_timezone_and_clock                        119     102     -17
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 0/3 up/down: 25/-48)            Total: -23 bytes
   text	   data	    bss	    dec	    hex	filename
1020753	    559	   5052	1026364	  fa93c	busybox_old
1020708	    559	   5052	1026319	  fa90f	busybox_unstripped

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/ntpd.c b/networking/ntpd.c
index 032dc51..06f6017 100644
--- a/networking/ntpd.c
+++ b/networking/ntpd.c
@@ -1147,8 +1147,7 @@
 	gettimeofday(&tvc, NULL); /* never fails */
 	dtime = tvc.tv_sec + (1.0e-6 * tvc.tv_usec) + offset;
 	d_to_tv(dtime, &tvn);
-	if (settimeofday(&tvn, NULL) == -1)
-		bb_simple_perror_msg_and_die("settimeofday");
+	xsettimeofday(&tvn);
 
 	VERB2 {
 		tval = tvc.tv_sec;