pattern.c depended on stick_table while in fact it should be the opposite.
So we move from pattern.c everything related to stick_tables and invert the
dependency. That way the code becomes more logical and intuitive.
This converter can be applied on top of an IPv4-type pattern. It
applies a netmask which is suited for IP address storage and matching.
This can be used to make all hosts within a certain mask to share the
same table entries and as such use the same server.
The mask can be passed in dotted form (eg: 255.255.255.0) or in CIDR
form (eg: 24).
Some converters will need one or several arguments. It's not possible
to write a simple generic parser for that, so let's add the ability
for each converter to support its own argument parser, and call it
to get the arguments when it's specified. If unspecified, the arguments
are passed unmodified as string+len.
The pattern type converters currently support a string arg and a length.
Sometimes we'll prefer to pass them a list or a structure. So let's convert
the string and length into a generic void* and int that each converter may
use as it likes.
