Feature request: Add support for CS16

[unixpunk]

Just making my request 'official'. :) Happy to help/donate where I can, but unfortunately not a programmer. This change could help reduce overall CPU usage of all csdr processes, not to mention also whichever tool is used to provide the I/Q data, i.e., rtl_sdr, rx_sdr or hackrf_transfer. (Where supported, obviously. I can confirm rx_sdr supports this as long as the device backed by SoapySDR also does.)