Fix for bug #12956: cast make differ rounding.

sql/item_func.cc:
  Fix for bug #12956: cast make differ rounding.
  - call rint() as we do in the Field_*int*::store(double)

mysql-test/r/ps.result

@@ -337,7 +337,7 @@ set @precision=10000000000;
 select rand(), 
 cast(rand(10)*@precision as unsigned integer) from t1;
 rand()	cast(rand(10)*@precision as unsigned integer)
--	6570515219
+-	6570515220
 -	1282061302
 -	6698761160
 -	9647622201
@@ -348,23 +348,23 @@ prepare stmt from
 set @var=1;
 execute stmt using @var;
 rand()	cast(rand(10)*@precision as unsigned integer)	cast(rand(?)*@precision as unsigned integer)
--	6570515219	-
+-	6570515220	-
 -	1282061302	-
 -	6698761160	-
 -	9647622201	-
 set @var=2;
 execute stmt using @var;
 rand()	cast(rand(10)*@precision as unsigned integer)	cast(rand(?)*@precision as unsigned integer)
--	6570515219	6555866465
--	1282061302	1223466192
--	6698761160	6449731873
+-	6570515220	6555866465
+-	1282061302	1223466193
+-	6698761160	6449731874
 -	9647622201	8578261098
 set @var=3;
 execute stmt using @var;
 rand()	cast(rand(10)*@precision as unsigned integer)	cast(rand(?)*@precision as unsigned integer)
--	6570515219	9057697559
+-	6570515220	9057697560
 -	1282061302	3730790581
--	6698761160	1480860534
+-	6698761160	1480860535
 -	9647622201	6211931236
 drop table t1;
 deallocate prepare stmt;

mysql-test/t/count_distinct3.test

@@ -17,7 +17,7 @@ while ($1)
   SET @rnd= RAND();
   SET @id = CAST(@rnd * @rnd_max AS UNSIGNED);
   SET @id_rev= @rnd_max - @id;
-  SET @grp= CAST(128.0 * @rnd AS UNSIGNED); 
+  SET @grp= CAST(127.0 * @rnd AS UNSIGNED); 
   INSERT INTO t1 (id, grp, id_rev) VALUES (@id, @grp, @id_rev); 
   dec $1;
 }

sql/item_func.cc

@@ -735,7 +735,7 @@ longlong Item_func_numhybrid::val_int()
   case INT_RESULT:
     return int_op();
   case REAL_RESULT:
-    return (longlong)real_op();
+    return (longlong) rint(real_op());
   case STRING_RESULT:
   {
     int err_not_used;