NEW comms/rtl_433

Hi,

attached a port of the rtl_433 tool.

cat pkg/DESCR

rtl_433 (despite the name) is a generic data receiver, mainly for the
433.92 MHz, 868 MHz (SRD), 315 MHz, 345 MHz, and 915 MHz ISM bands,
utilizing rtl-sdr devices.

I don't think it's overly useful to @sample all those example files 

to /etc/rtl_433, therefore I only left a comment about them in the README.

I had some issues (RTL-SDR blog v3) with the default sample rate rtl_433 uses being too high, therefore a section covering the topic was added to the README.

To get the manual page installed into the proper location, I had to patch, don't 

know if there's an easier way with CONFIGURE_ARGS or environment variables.

This will also be a RUN_DEPEND for the upcoming net/kismet update I have in

the queue, which needs a little cleanup before I send it here.

Tarball attached.

Any kind of feedback, test reports, or even OKs would be greatly appreciated.

cheers,

Sebastian