Increase table comment print size to 500 bytes to be able to print more foreign key constraint infos
ha_innobase.h:
  Change max key len back to 500 bytes because MySQL interpreter cannot handle more


sql/ha_innobase.h:
  Change max key len back to 500 bytes because MySQL interpreter cannot handle more
sql/ha_innobase.cc:
  Increase table comment print size to 500 bytes to be able to print more foreign key constraint infos