lp:731815 Crash/valgrind warning Item::send with 5.1-micro

Two problems:
* Item_func_convert_tz() did not tell args[0] that it needs
  TIME_NO_ZERO_IN_DATE result
* Item_func_timediff did not respect fuzzy_date limitations,
  truncated seconds when casting to signed long, resulting in
  invalid time value (hours, seconds = (uint)-1).

mysql-test/r/func_time.result

@@ -1468,3 +1468,11 @@ Warnings:
 Warning	1292	Incorrect datetime value: '0'
 Warning	1292	Incorrect datetime value: '0'
 drop table t1;
+select timediff('0000-00-00 00:00:00', cast('2008-03-26 07:09:06' as datetime));
+timediff('0000-00-00 00:00:00', cast('2008-03-26 07:09:06' as datetime))
+-838:59:59.999999
+Warnings:
+Warning	1292	Truncated incorrect time value: '-596523:14:07'
+select convert_tz(timediff('0000-00-00 00:00:00', cast('2008-03-26 07:09:06' as datetime)), 'UTC', 'Europe/Moscow');
+convert_tz(timediff('0000-00-00 00:00:00', cast('2008-03-26 07:09:06' as datetime)), 'UTC', 'Europe/Moscow')
+NULL

mysql-test/t/func_time.test

@@ -910,3 +910,9 @@ select last_day(f2) from t1;
 select last_day(f2) from t1 where last_day(f2) is null;
 select * from t1 order by last_day (f2);
 drop table t1;
+
+#
+# lp:731815 Crash/valgrind warning Item::send with 5.1-micro
+#
+select timediff('0000-00-00 00:00:00', cast('2008-03-26 07:09:06' as datetime));
+select convert_tz(timediff('0000-00-00 00:00:00', cast('2008-03-26 07:09:06' as datetime)), 'UTC', 'Europe/Moscow');

sql/item_timefunc.cc

@@ -1872,7 +1872,8 @@ bool Item_func_convert_tz::get_date(MYSQL_TIME *ltime,
     to_tz_cached= args[2]->const_item();
   }
 
-  if (from_tz==0 || to_tz==0 || get_arg0_date(ltime, TIME_NO_ZERO_DATE))
+  if (from_tz==0 || to_tz==0 ||
+      get_arg0_date(ltime, TIME_NO_ZERO_DATE | TIME_NO_ZERO_IN_DATE))
   {
     null_value= 1;
     return 1;
@@ -2534,6 +2535,9 @@ bool Item_func_timediff::get_date(MYSQL_TIME *ltime, uint fuzzy_date)
       l_time1.time_type != l_time2.time_type)
     goto null_date;
 
+  if (fuzzy_date & TIME_NO_ZERO_IN_DATE)
+    goto null_date;
+
   if (l_time1.neg != l_time2.neg)
     l_sign= -l_sign;
 
@@ -2550,8 +2554,12 @@ bool Item_func_timediff::get_date(MYSQL_TIME *ltime, uint fuzzy_date)
   if (l_time1.neg && (seconds || microseconds))
     l_time3.neg= 1-l_time3.neg;         // Swap sign of result
 
+  set_if_smaller(seconds, INT_MAX32);
   calc_time_from_sec(&l_time3, (long) seconds, microseconds);
 
+  if ((fuzzy_date & TIME_NO_ZERO_DATE) && (seconds == 0) && (microseconds == 0))
+    goto null_date;
+
   *ltime= l_time3;
   check_time_range(ltime, &was_cut);