Problem: getting an autoincrement value for a partition table in the ::info() method we call
the get_auto_increment() for all partitions. That may cause a problem for at least MyISAM
tables that rely on some table state (in this particular case table->naxt_nuber_field is 
set to 0 in the mysql_insert() and we get a crash). 
Moreover, calling get_auto_increment() is superfluous there.

Fix: use ::info(HA_STATUS_AUTO) calls to get autoincrement values for partitions instead of
get_auto_increment() ones in the ha_partition::info().