* Added new hackrf_error especially for streaming to return more details.
* Adding management of usb transfer cancelled for hackrf_stop_rx()/hackrf_stop_tx().
* Added robustness on hackrf_close() to correctly close libusb related stuff even if USB device is removed or other problems.
* Fixed threading problems (start, stop() then start() ...).
* Cleanup the whole code.
Add max2837_set_lpf_bandwidth() function to choose available LPF filter bandwidth based on bandwidth in Hz.
Change configuration of MAX2837 to set LPF_EN and FT at max2837_setup(), not in max2837_rx() or max2837_tx() (which was overriding prior filter configuration).
Implement switching between several supported sampling rates for Jellybean and Jawbreaker.
Commit bits of the Si5351C USB request support that I apparently missed in a prior commit.
