airodump-ng: sometimes show wrong channel when network not have a valid essid

[m4tr1x]

hi,
sometimes airodump-ng show wrong channel when it found a network with hidden/invalid essid (ex.: <length: 0>).
This bug it's related to bad radiotap parsing,
the result it's a wrong converted value (133, 108, etc...)
Good work

[misterx]

See also #647.

[m4tr1x]

if you convert the bad value with this macro:

#define EXTRACT_16BITS(p) \
                      ((u_int16_t)((u_int16_t)*((const u_int8_t *)(p) + 1) << 8 | \
                      (u_int16_t)*((const u_int8_t *)(p) + 0)))

the result is a valid 802.11b/g channel

[someone]

It might be in osdep/byteorder.h:

#define ___my_swab16(x)