Working ADC3 driver for 9XE additional analog inputs (driver source base...

...d on Michael Blandford's code)

This pull adds S4 (potentiometer 4), and two sliders (LS2 and RS2) to existing code for 9XE.

Known bugs:
* missing string definitions for other languages (only en defined)
* switch autosource always returns SE (probably not related to this changes)
* only four sliders drawn on main screen (LS, LS2, RS, RS2)

I probably missed some spots in existing code where new pot/sliders should be used. Only tested on 9XE!