Prevent event code collisions when using Polycode stock classes by adding a class-unique EVENTBASE_ constant to each class's event types. (The EVENTBASE_s are documented in PolyEvent.h.) Make a small change to create_lua_library to support the EVENTBASE_ idiom.
Merge pull request #157 from mcclure/uniqueevents

Prevent event-code collisions when using Polycode stock classes