Don't write out states if they haven't changed

sql/sql_base.cc:
  Call extra(HA_EXTRA_PREPARE_FOR_DROP) before doing a drop of a table
  More DBUG
sql/sql_table.cc:
  Call extra(HA_EXTRA_PREPARE_FOR_RENAME) before renaming a table
storage/maria/ha_maria.cc:
  Ensure that file->trn is set when we call extra(HA_EXTRA_PREPARE_FOR_DROP/RENAME)
storage/maria/ma_close.c:
  When doing close, assert if we have pointers in trn->table_list that points to the MARIA_SHARE
storage/maria/ma_extra.c:
  Reset info->state_start in case of drop/rename. This fixes the problem of accessing freed memory in repair
  Don't write state changed if they haven't changed
storage/maria/ma_open.c:
  Reset share->changed after we have written out a state (speed optimization to not write states when they haven't changed)
storage/maria/ma_state.c:
  Decrement share->in_trans properly in DBUG_BINARY to ensure that the DBUG_ASSERT() in maria_close() works
  More DBUG