bladeRF-cli: Disable 'recover' command when not building against libusb
libbladeRF: Added dummy backend

This allows libbladeRF to be built with no other backends, which is
generally only useful when working on new backends.
libbladeRF: Replaced hard-coded timeout with configured value

Upon a stream callback, the timeout stored in the device handle is now
used instead of a hardcoded value.

Renamed the macro for the ctrl xfer timeout to be consistent with its
bulk counterpart.
libbladeRF-sync: Drafted API header
libbladeRF-sync: Added start(), stop(), version() prototypes
common: [WIP] Added a simple FIFO implementation
libbladeRF-sync: Touched up a few typos
libbladeRF_sync: Stubbed out top-level interface to allow library build
libbladeRF_sync: Renamed directory
libbladeRF_sync: Renamed flag bitmasks
libbladeRF_sync: Added sources to build. Removed start/stop fns
libbladeRF_sync: Added test program
libbladeRF_sync: [WIP] Working on RX
libbladeRF_sync: [WIP] Debugging RX worker startup/shutdown
libbladeRF_sync: Changed flawed requests scheme to resolve race
libbladeRF_sync: [WIP] Started working on RX stream
libbladeRF_sync: RX path in place, debugging required

fifo.c implementation appears to have some memory corruption defects,
and we may be trying to free() items before the worker thread has
joined.
libbladeRF_sync: Moved callbacks into worker.c, fixed mem bugs
libbladeRF_sync: Cleaned up worker state check
Implemented RX-portion of test application, added TX impl to lib

The former appears to run fine, minus an initial set of 0-samples.
The latter requires additional debugging. (memory corruption)