Fixed issues found by buildbot & valgrind:

- Wrong thd uses in Item_subselect, could lead to crash
- Inititalize uninitialized variable in new autoincrement handling code


sql/handler.cc:
  More DBUG_PRINT
sql/item_subselect.cc:
  Wrong thd uses in Item_subselect, could lead to crash
storage/innobase/handler/ha_innodb.cc:
  Initialize variable needed by upper level. This only happens when auto-increment value wraps over.
storage/xtradb/handler/ha_innodb.cc:
  Initialize variable needed by upper level. This only happens when auto-increment value wraps over.

sql/handler.cc

@@ -2621,7 +2621,8 @@ int handler::update_auto_increment()
   if (unlikely(nr == ULONGLONG_MAX))
       DBUG_RETURN(HA_ERR_AUTOINC_ERANGE);
 
-  DBUG_PRINT("info",("auto_increment: %lu", (ulong) nr));
+  DBUG_PRINT("info",("auto_increment: %llu  nb_reserved_values: %llu",
+                     nr, nb_reserved_values));
 
   /* Store field without warning (Warning will be printed by insert) */
   save_count_cuted_fields= thd->count_cuted_fields;

sql/item_subselect.cc

@@ -220,7 +220,7 @@ bool Item_subselect::fix_fields(THD *thd_param, Item **ref)
   uint8 uncacheable;
   bool res;
 
-  status_var_increment(thd->status_var.feature_subquery);
+  status_var_increment(thd_param->status_var.feature_subquery);
 
   DBUG_ASSERT(fixed == 0);
   engine->set_thd((thd= thd_param));

storage/innobase/handler/ha_innodb.cc

@@ -10284,6 +10284,7 @@ ha_innobase::get_auto_increment(
                    take care of this */
                 prebuilt->autoinc_last_value = 0;
                 dict_table_autoinc_unlock(prebuilt->table);
+                *nb_reserved_values= 0;
                 return;
         }
 	*nb_reserved_values = trx->n_autoinc_rows;

storage/xtradb/handler/ha_innodb.cc

@@ -11225,6 +11225,7 @@ ha_innobase::get_auto_increment(
                    take care of this */
                 prebuilt->autoinc_last_value = 0;
                 dict_table_autoinc_unlock(prebuilt->table);
+                *nb_reserved_values = 0;
                 return;
         }
 	*nb_reserved_values = trx->n_autoinc_rows;
@@ -13019,7 +13020,7 @@ static	MYSQL_SYSVAR_ENUM(corrupt_table_action, srv_pass_corrupt_table,
   "Warn corruptions of user tables as 'corrupt table' instead of not crashing itself, "
   "when used with file_per_table. "
   "All file io for the datafile after detected as corrupt are disabled, "
-  "except for the deletion.",
+  "except for the deletion. Possible options are 'assert', 'warn' & 'salvage'",
   NULL, NULL, 0, &corrupt_table_action_typelib);
 
 static MYSQL_SYSVAR_ULINT(lazy_drop_table, srv_lazy_drop_table,