[AD] Windows keyboard fixes, two patches

[torhu <torhu.lists@xxxxxxxxxx>]

See http://www.allegro.cc/forums/thread/607673/1

numpad.diff - New system for mapping extended keys.  Mainly for getting 
the same keycode for numpad keys independently of the state of Num Lock.

modifiers.diff -  More reliable updating of the toggle modifiers.


Tested on Windows 7, seems to work just fine.  Is this okay to check in?

Attachment: modifiers.diff
Description: /

Attachment: numpad.diff
Description: /