Generate modified FS-GT3B firmware

Takes original firmware in S19 format (length of file is 77836 bytes), checks if original firmware is compatible with modifications and applies selected modifications. New firmware should have length 77836 bytes also (check it if it is correct).

original firmware file in .s19 format:

repairs of not working things

repair bad EXPOs

correct showed E.POINT values when switching models

new functions/limits

trims range -99 to 99 with finer step (1.5us instead of 2.5us)

set backlight to arbitrary value (in seconds)

set battery low voltage warning

disable autorepeat of trim buttons (changing values while button is pressed)

disable autorepeat of D/R buttons (changing values while button is pressed)

make CH3 button momentary (value is changed only while pressed)

set max endpoint to given value, higher values can be dangerous and are also limited by VF module

use CH2 expo setting for throttle expo and CH3 expo setting for brake expo