[airodump-ng] - added support for json file export

[TheRinger]

[airodump-ng] - added support for json file export

-- added 'json' option to --output-format
files modified:
src/airodump-ng.c
src/airodump-ng.h

[TheRinger]

Compiles and runs but getting this error on rpi3, any ideas?

CC airodump_ng-airodump-ng.o
airodump-ng.c: In function ‘dump_write_json’:
airodump-ng.c:4567:37: warning: pointer targets in passing argument 1 of ‘format_text_for_csv’ differ in signedness [-Wpointer-sign]
temp = format_text_for_csv(st_cur->probes[i], st_cur->ssid_length[i]);
^~~~~~
airodump-ng.c:4292:7: note: expected ‘const unsigned char *’ but argument is of type ‘char *’
char *format_text_for_csv(const unsigned char *input, int len)
^~~~~~~~~~~~~~~~~~~
CCLD airodump-ng