Fixing and improving SDR support (SoapySDR and UHD)

- Soapy SDR now works.
- Channels can be selected.
- Antennas can be listed and selected.
- Device args, tune args, stream args can be specified.

src/common/debug.h

@@ -21,6 +21,7 @@
 #define DSMS		14
 #define DSDR		15
 #define DUHD		16
+#define DSOAPY		17
 
 #define PDEBUG(cat, level, fmt, arg...) _printdebug(__FILE__, __FUNCTION__, __LINE__, cat, level, -1, fmt, ## arg)
 #define PDEBUG_CHAN(cat, level, fmt, arg...) _printdebug(__FILE__, __FUNCTION__, __LINE__, cat, level, CHAN, fmt, ## arg)