- 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.
get-wm-hints, set-wm-normal-hints!, get-wm-normal-hints,
create-gcontext, change-gcontext, get-visual-info,
change-window-attributes, get-window-attributes, configure-window,
create-window to use an enumerated type instead of symbols.
- renamed functions in xlib-client (e.g. wm-hints to get-wm-hints).
frese