implement simple sampler

Simple sampler to use in games. This is basic since the test_sampler
does not use SDcard (to be tested & implemented).
Merge remote-tracking branch 'pulkomandy/master'
rework device input in emulator

- added event handling as an engine (since it's on top of the kernel)
- added events for keyboard (keycodes to be tested), mouse
- added handling of mouse_data (buttons & co)
- added proper joystick/gamepad handling
- game pad emulation is done in games via evt_ functions, not in
emulator level
added pulkomandy in AUTHORS file
2D version of the text buffer

fixed the size as well, it's now 80x30
added print_at and simple text window drawing functions
started emulator keyboard tables

reverse keyboard tables SDL scancode to USB Boot protocol(tedious...)
print_at: don't copy NULL char at end of string
test_usb: more graphical view of gamepad.
Add analog pad view (untested, no hardware!)