Change POINT to return the colour index, not the (r,g,b) value

[breakintoprogram]

Point currently returns the RGB value of the pixel. Modify to return the index in the VDP palette

[breakintoprogram]

This requires a change to the VDP and MOS (to return the colour index) and a modification to BBC BASIC.
NB:

• The RGB values of the colour are still available to BASIC in the system variables area.
• As some colours (index > 16) are duplicated, the function will return the first value found, i.e. bright white = 15 and 79.

[breakintoprogram]

Testing critera:

• Does it work in non-palette mode - yes, with the above caveats
• Does it work in palette mode - probably won't, as the palette lookup is not modified with the palette information