#81 use x11 keysym's for keyboard input

[Rick Altherr]

This patch changes the x11 input handling to use KeySyms instead
of raw device keycodes. This gives a device independent
keyboard mapping instead of the x86 specific mapping that was
there previously.

Also note that if someone knows the ADB keycode for the
Command key, it can easily be mapped to the META key (windows
key or Command key depending on hardware).

This patch allows the keyboard to work correctly on OS X and
should also let it work on any system using X11.

[Rick Altherr]