The IEEE 802.15.4 kernel stack doesn't implement ACKs yet and prints
a warning if we request them. Since dirtpan has its own ACKs, we
just disable IEEE 802.15.4 ACKs for now.
- dirtpan.c (debug_ip): only dump local packets if debug > 1
- dirtpan.c (debug_dirt): dump packet content only if debug > 1
- dirtpan.c (debug_dirt): made packet content dump more readable
- dirtpan.c (debug_dirt): added terse debug output for debug == 1
- dirtpan.c (usage): doubling -d now has a meaning