SM6FBQ / HackRF clone - History

Clock reference: Add UI hook. Simplify selection code.

PortaPack: Make label-drawing functions take a label enum.

PortaPack: Improve speed of frequency rendering.

To reduce impact on hackrf_sweep speed.

PortaPack: Double draw speed of UI, which was impacting hackrf_sweep.

Clock reference: Return enum for selected clock source.

PortaPack: Add check for PortaPack clock reference, use if present.

Wow, it takes a lot of ugly code to keep blinky happy...

Si5351C: Extract best block source function into hackrf_core.

It's not an Si5351C driver thing, but a HackRF thing. Also added a driver function to check if CLKIN signal is valid, and made use of it, instead of opaque register read code.