probability: add computation of OFDM frame error rate

This adds code to generate frame error probabilities based on OFDM
and error-correction characteristics of 802.11a rates, assuming
AWGN.  Very much a WIP, but the output looks reasonable.
config: use "long int" as required by my version of libconfig

Fixes:

config.c: In function ‘load_config’:
config.c:222: warning: passing argument 3 of ‘config_lookup_int’ from incompatible pointer type
/usr/include/libconfig.h:235: note: expected ‘long int *’ but argument is of type ‘int *’
config.c:245: warning: passing argument 3 of ‘config_lookup_int’ from incompatible pointer type
/usr/include/libconfig.h:235: note: expected ‘long int *’ but argument is of type ‘int *’
probability: use a faster binomial coefficient calculation

Computing with factorials is just horrendously slow, especially when
not factored; use the iterated multiplication definition instead.
Revert "config: use "long int" as required by my version of libconfig"

This reverts commit 07bcc14e93564533261dbaec9080a383334323dc.
hook up per model and move to libevent
drand48 is a thing
remove some dead code
remove probability matrix

Instead, we will derive probabilities from stations' SNRs
drop mac80211_hwsim
whitespace cleanup
add a netlink callback for error messages
remove some debug cruft
don't use a struct for mac addresses, just use u8 arrays
rearchitect wmediumd to enable time-based delivery

This adds a queue for frames and a timerfd based scheduler
which will eventually allow setting frames to be 'delivered'
after a certain amount of time to simulate latency and
throughput.
add list.h
get rid of malloc for tx rates
use the sender sent by nl80211 rather than src in the frame