The existing RTL TCP driver is quite different from its brother RTL_SDR.
It's much more complicated, uses gr::blocks::deinterleave and
gr::blocks::float_to_complex, and generally doesn't work correctly
(e.g. https://github.com/csete/gqrx/issues/99
Spectrum is mirrored when filter or demodulator changes (rtl_tcp) #99)
I've converted the RTL TCP driver to the model used by RTL_SDR,
simplifying it in the process, and fixing the GQRX issue.
For use with the rtl_tcp utility acting as a spectrum server.
The "empty" rtl_tcp= device hint might be used to connect to rtl_tcp
running on local machine.