- changed error and after-function handling a bit
- added screen caching
- added timeout in wait-event implementation (did not work with multiple threads)
- replaced most of symbol or symbol list arguments by enumerated types,
enum-sets and alists of enumerated types.
- reformed event representation. Every event has it's own record-type now.
and points to pairs (x . y). Added some auxiliary functions for that.
+ text: made the format arguments optional, and default to '1-byte.
+ added comments.