Bug #33796 Memory leak for prepared statements in embedded server.

Field data for a query was stored to the stmt->alloc that is emptied
with mysql_stmt_close statement only. That means a lot of memory can
be occupied without a reason if used doesn't call mysql_stmt_close often.

libmysql/libmysql.c

@@ -4522,14 +4522,11 @@ my_bool STDCALL mysql_stmt_free_result(MYSQL_STMT *stmt)
   {
     MYSQL *mysql= stmt->mysql;
 
-    if (result->data)
-    {
     /* Result buffered */
     free_root(&result->alloc, MYF(MY_KEEP_PREALLOC));
     result->data= NULL;
     result->rows= 0;
     stmt->data_cursor= NULL;
-    }
 
     if (mysql && stmt->field_count &&
         (int) stmt->state > (int) MYSQL_STMT_PREPARE_DONE)

libmysqld/lib_sql.cc

@@ -668,7 +668,7 @@ bool Protocol::send_fields(List<Item> *list, uint flag)
     DBUG_RETURN(0);
 
   field_count= list->elements;
-  field_alloc= thd->current_stmt ? &thd->current_stmt->mem_root :
+  field_alloc= thd->current_stmt ? &thd->current_stmt->result.alloc :
                                    &mysql->field_alloc;
   if (!(client_field= mysql->fields= 
 	(MYSQL_FIELD *)alloc_root(field_alloc,