null.result, null.test:

   Fix for a bug #2219, regarding a bad cast to integer from NULL
item_func.h:
  Fix for a bug #2219, regarding a bad cast to integer from NULL
sql_parse.cc:
  A fix for a bug #2207, with mysql server haning on option setting

mysql-test/r/null.result

@@ -153,3 +153,6 @@ explain select * from t1 where a between 2 and 3 or b is null;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	idx	idx	4	NULL	2	Using where
 drop table t1;
+select cast(NULL as signed);
+cast(NULL as signed)
+NULL

mysql-test/t/null.test

@@ -97,3 +97,4 @@ insert into t1 values
 explain select * from t1 where a between 2 and 3;
 explain select * from t1 where a between 2 and 3 or b is null;
 drop table t1;
+select cast(NULL as signed);

sql/item_func.h

@@ -212,8 +212,8 @@ class Item_func_signed :public Item_int_func
 {
 public:
   Item_func_signed(Item *a) :Item_int_func(a) {}
-  double val() { return args[0]->val(); }
-  longlong val_int() { return args[0]->val_int(); }
+  double val() {  null_value=args[0]->null_value; return args[0]->val(); }
+  longlong val_int() {  null_value=args[0]->null_value; return args[0]->val_int(); }
   void fix_length_and_dec()
   { max_length=args[0]->max_length; unsigned_flag=0; }
   void print(String *str);
@@ -224,8 +224,8 @@ class Item_func_unsigned :public Item_int_func
 {
 public:
   Item_func_unsigned(Item *a) :Item_int_func(a) {}
-  double val() { return args[0]->val(); }
-  longlong val_int() { return args[0]->val_int(); }
+  double val() { null_value=args[0]->null_value; return args[0]->val(); }
+  longlong val_int() { null_value=args[0]->null_value; return args[0]->val_int(); }
   void fix_length_and_dec()
   { max_length=args[0]->max_length; unsigned_flag=1; }
   void print(String *str);

sql/sql_parse.cc

@@ -1624,9 +1624,11 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     switch (command) {
     case MYSQL_OPTION_MULTI_STATEMENTS_ON:
       thd->client_capabilities|= CLIENT_MULTI_STATEMENTS;
+      send_eof(thd);
       break;
     case MYSQL_OPTION_MULTI_STATEMENTS_OFF:
       thd->client_capabilities&= ~CLIENT_MULTI_STATEMENTS;
+      send_eof(thd);
       break;
     default:
       send_error(thd, ER_UNKNOWN_COM_ERROR);