This patch does not change any algorithms or code paths, it just moves the transaction-related methods in the drizzled/ha_commands.cc file into a file named drizzled/transaction_services.cc and creates a singleton Service class called TransactionServices containing all the previous ha_xxx methods related specifically to the XA distributed transaction processing model.
This is a quick stopgap patch in the move towards separating out the XA Resource Manager API from the Storage Engine API.