Bug #28005 Partitions: can't use -9223372036854775808

the Item_neg changes INT_RESULT with DECIMAL_RESULT when
it gets this border value, what is not necessary.

mysql-test/r/partition.result

@@ -1233,4 +1233,6 @@ select * from t1;
 c1	c2
 aaa	2
 drop table t1;
+create table t1 (s1 bigint) partition by list (s1) (partition p1 values in (-9223372036854775808));
+drop table t1;
 End of 5.1 tests

mysql-test/t/partition.test

@@ -1441,5 +1441,11 @@ insert into t1 values ('aaa','1') on duplicate key update c2 = c2 + 1;
 select * from t1;
 drop table t1;
 
+#
+# Bug #28005 Partitions: can't use -9223372036854775808 
+#
+
+create table t1 (s1 bigint) partition by list (s1) (partition p1 values in (-9223372036854775808));
+drop table t1;
 
 --echo End of 5.1 tests

sql/item_func.cc

@@ -1483,7 +1483,7 @@ void Item_func_neg::fix_length_and_dec()
   */
   if (hybrid_type == INT_RESULT &&
       args[0]->type() == INT_ITEM &&
-      ((ulonglong) args[0]->val_int() >= (ulonglong) LONGLONG_MIN))
+      ((ulonglong) args[0]->val_int() > (ulonglong) LONGLONG_MIN))
   {
     /*
       Ensure that result is converted to DECIMAL, as longlong can't hold