hnbgw: add cmdline arg parsing with default options

Default options taken from osmo-nitb:

    -h --help                  This text.
    -d option --debug=DHNBAP:DSUA:DRUA:DRANAP:DMAIN  Enable debugging.
    -D --daemonize             Fork the process into a background daemon.
    -s --disable-color
    -T --timestamp             Prefix every log line with a timestamp.
    -V --version               Print the version of OsmoHNBGW.
    -e --log-level number      Set a global loglevel.

Change-Id: I931cee01c605c1b507c16041ada226cf963ea433
1 file changed