Extend BBC BASIC to support setting of keyboard delay and rate, and get/set the LED state

[breakintoprogram]

*FX 11, n: Selects keyboard auto-repeat delay
*FX 12, n: Selects keyboard auto-repeat rate
*FX 118, n: Keyboard LED control

[breakintoprogram]

*FX 11, n: VDU 23, 0, 8, n; 0; 0xFF
*FX 12, n: VDU 23, 0, 8, 0; n; 0xFF
*FX 118, n: VDU 23, 0, 8, 0; 0; n

[breakintoprogram]

Also fixed *FX so that it can either:

• Accept 1 16-bit parameter -or-
• 2 8-bit parameters