added missing us to ticks macro
fix: 1s = 1000*1000us
nativenet clean up

Make nativenet tap payload type consistent with radio_packet_t
Also remove a trailing space
check payload length validity

make sure the payload does not exceed the amount of data received
Merge pull request #456 from mehlis/fix-ping

Fix ping
Merge pull request #479 from LudwigOrtmann/nativenet_lenchck

Nativenet length check and cleanup