Add some networking stuff: revip() and asn()

[fza]

I added two shorthand functions:

# Get information about an IP (ASN number, owner, etc.). Works with domains, too.
# It simply looks up the IP at spameatingmonkey.net over DNS. Does not work with IPv6, unfortunately.
$ asn 8.8.8.8
8.8.8.0/24 | AS15169 | Google Inc. | 2000-03-30 | US
$ asn github.com
192.30.252.0/24 | AS36459 | GitHub, Inc. | 2012-11-13 | US

# Return an IP address in reverse form. Works with IPv6, too. Actually this is a helper function for asn().
$ revip 1.2.3.4
4.3.2.1
$ revip 2a00:1450:4016:803::1008
8.0.0.1.0.0.0.0.0.0.0.0.0.0.0.0.3.0.8.0.6.1.0.4.0.5.4.1.0.0.a.2

The alias myasn echoes the ASN info for the current ip.

Maybe this is of interest for anyone :)