Add "class" that understands IPv4 addresses and subnet masks.

Add "class" that understands IPv4 addresses and subnet masks.
We now store IPv4 addresses in host order, allowing non-equivalence
comparisons. That is, display filters with lt, le, gt, and ge will work
on big-endian and little-endian machines.

CIDR notation is now supported for IPv4 addresses in display filters.
You can test to see if an IPv4 address is on a certain subnet by using
this notation. For example, to test for IPv4 packets on a Class-C network:

	ip.addr == 192.168.1.0/24

svn path=/trunk/; revision=1032