fjoy_disp now prints directly to lcd_memory instead of using LCD_Print.

This should make it faster. Also, made the printing function less
repetitive and more straightforward: this will allow for things like
temporarily displaying some different message (since fjoy_disp is always
reprinting everything and has total control over what it does).
Analog inputs in fjoy now have a selectable resolution. Interpolation and decimation order must be changed though.
Fixed calibration on fjoy!

Not only does it improve the joystick response, it also makes the
calibration independant of the final bit resolution used.