[FOSS-GPS] RTKLIB OpenWrt package

[Nuno Gonçalves]

I just commited a RTKLIB package to OpenWrt.

Routers like the TP-Link TL-WR703N or TP-Link TL-WR710N are cheaper
than a Beaglebone or Raspberry Pi so they are a excellent choice for
some applications.

I didn't tune the compile flags for size or performance. Maybe I will
try that in the future, or someone else.

For reference the binaries sizes on my router are:

convbin 581.9KB
pos2kml 441.1KB
rnx2rtkp 846.4KB
rtkrcv 1.0MB
str2str 774.0KB

Regards,
Nuno