Prompt-based event-loop, xcb-now, xcb-later
Renamed xcb-later to delay-reply, added with-replies (replacement for xcb-await).
.gitignore stuff
Rename with-event-loop to with-connection
Move win.scm to new event loop
Updated randr and tinywm examples
Shorten/format tinywm
Set minimum size for events/errors, in order to eventually support
SendEvent requests.

Refactor generic event loop code out into its own module (flow
event-loop)
Hide the interally-used tag in with-notifies
Made xcb-connection thread and interrupt safe
Mechanism to post functions to the event loop from another thread
More robust event dispatcher that routes events based on guard functions
- Ensure connection mutex is unlocked when exceptions occur
- Fix bug in 1-byte long requests (i.e. Bell)
- Delete pending continuations by calling `unsolicit'
- Fix duplicate tag problem in with-replies
- Async procs run inside a prompt
- Flush output directly to the socket rather than to a custom binary output port
Fix bug in assigning values to enum members
- Revamped `with-replies' to use a procedure in flow/event-loop called
  `notify-map' as its basis, moved `with-replies' to xcb/event-loop

- Slight modification to error handling code; still not ideal

- Added `create-listener' syntax, which groups event listeners
  together with procedures to stop/reset them
Expose procedures xenum-keys, xenum-values, which return the keys and
values of an xcb enum, respectively.
- Remove custom binary port wrappers from xcb connections
- Instead, just wrap reading X connection setup info in a custom binary port
Add missing files to make clean target