new input system

new input system

  This patch replaces keyboard.js with keymap.js and input.js, introducing
a substantial rewrite of the input system which addresses several
long-standing bugs and feature requests, and puts the framework in place
for others.

http://bugs.conkeror.org/issue159  $fallthrough and keydown events

  Fixed, by a new mechanism for explicitly allowing keydown and keyup
events.  Function `define_fallthrough' implements this.

http://bugs.conkeror.org/issue146  'f' and 'C-u f' don't work on Slashdot articles

  Fixed.

http://bugs.conkeror.org/issue92  M-x cannot call prefix commands

  Fixed.

http://bugs.conkeror.org/issue22  Mouse clicks integrated into key binding system

  Preliminary support for mouse bindings.  Completing this will entail
improving the input-mode system, to set the proper keymaps for mouse
actions.