libbb: introduce and use xgettimeofday(), do not truncate 64-bit time_t in shells

function                                             old     new   delta
xgettimeofday                                          -      11     +11
get_local_var_value                                  280     281      +1
svlogd_main                                         1323    1322      -1
change_epoch                                          67      66      -1
timestamp_and_log                                    461     458      -3
hwclock_main                                         301     298      -3
fmt_time_bernstein_25                                135     132      -3
step_time                                            331     326      -5
script_main                                         1207    1202      -5
machtime                                              34      28      -6
curtime                                               61      54      -7
ts_main                                              423     415      -8
nmeter_main                                          761     751     -10
gettime1900d                                          67      46     -21
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/12 up/down: 12/-73)           Total: -61 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/libbb/xfuncs_printf.c b/libbb/xfuncs_printf.c
index aea995a..99596b9 100644
--- a/libbb/xfuncs_printf.c
+++ b/libbb/xfuncs_printf.c
@@ -720,3 +720,14 @@
 	if (settimeofday(tv, NULL))
 		bb_simple_perror_msg_and_die("settimeofday");
 }
+
+void FAST_FUNC xgettimeofday(struct timeval *tv)
+{
+#if 0
+	if (gettimeofday(tv, NULL))
+		bb_simple_perror_msg_and_die("gettimeofday");
+#else
+	/* Never fails on Linux */
+	gettimeofday(tv, NULL);
+#endif
+}