Subnet matching

Thanks for this module, and especially for the 2.x version.
I've some issues with it I'll try to solve (see #1271756: Wrong links to user account pages on subsites → and ✨ User ordering when multiple matches exists Closed: outdated ).

I needed subnet matching (see CIDR notation) in my project.
I've modified the ip_login_check() function to use ip2long. I think it allows better validation and matching.

Using the patch below you can specify the following address patterns:

• Single IPv4 address
• * wildcard, e.g. 192.168.100.*
• IPv4 address range in the form of IP1 - IP2, e.g. 192.168.100.1 - 192.172.200.1
• and finally, my favorite: IPv4 subnet in the form of 192.168.100.1/16

Patch file attached and needs to be reviewed.