HTTP control port for whiteboxd

* Latency controllable down to the ms.
* Add pdma_clear and properly clear the transmit chain for PTT.
* Fix PDMA ping-pong undefined state.
* Add poll and tie into daemon main event loop.
* Add http parsing routines.
* Fix round-off issues with software based DDS.
* Test for PTT operation.
* Parameter to use CMX991's PLL or not.