* in drizzled/lock.cc, the involved_engines calculation was incorrectly using getSlot() instead of the new unified MonitoredInTransaction::getId() method for determining uniqueness. * Removed InnoDB's trx_t's active_trans data member. Now using only trx_t's conc_state member to determine state of the transaction (imagine that.) Added asserts() to test some assumptions about when and how a trx_t's conc_state can and cannot be in TRX_NOT_STARTED state. * Remove getSlot() from plugin::StorageEngine.