setup 'share' struct for all partiton file elements. It's neccessary because we use
m_file[0]->update_create_info(create_info) during ha_partition::update_create_info
and 'share' for m_file[0] should be valid


sql/ha_partition.h:
  Bug#20548 Events: crash if InnoDB, multiple events, busy procedures, partitions
sql/handler.h:
  Bug#20548 Events: crash if InnoDB, multiple events, busy procedures, partitions