B210 USRP appears as a 2-channel device by default. We prevent weird
application behavior by restricting the number of connected channels to
the value given via nchan= argument (1 by default).
since dc offset / iq imbalance is not implemented for recent USRPs this
might cause undesired behavior in GRC. As a workaround we do not pass
them to the caller but print them to the stderr.
This patch-set adds substantial new support for UHD features relating to
wire-format, time-synchronization, and refclock/PPS.
It is intended for both sources and sinks. The get-precision-time
function I simply made static and copied into both source and sink
files. It really belongs in osmosdr utiltiies, it uses Boost to hide the
Windows-vs-Unix-like precision time "goop".