Switch to the newer API call which can provide a list of ranges.
There are feature detection ifdefs provided by the library
so that code will always correctly compile.
The soapysdr range type does not provide a step size,
however apps like the osmocom siggen use this size for a slider,
and a value of zero will cause a divide by zero error.
Although many ranges are not actually linear,
the idea to provide some default step to avoid crashes.
A future addition to the API may include providing a step.
When the special 0.0 bandwidth setting is used, set the filter bandwidth to rate * 0.75.
Passing automatic 0.0 bandwidth for some devices was problematic.
The automatic IQ balance mode is not supported,
but we should not throw when it is set to disabled.
Setting to disabled is techinically allowable,
and currently throwing is disruptive for users.
Josh Blum