Reduce code size of the firewall.

[hlef]

The firewall is a little bit too big. Reduce the code size by...

• Removing the template in EndpointsTable. Instead, go for a fixed-size buffer that can contain both IPV4 and IPV6 addresses.
• Simplify find_endpoint and remove_endpoint which rely on large templated C++ utility functions.

With this, we gain about 2kB.

[davidchisnall]

This wastes a lot of space for IPv4 addresses. I would still like separate arrays for each, I just want them sorted / searched with something like qsort (sort variable-sized things taking the size as an argument, using memcmp rather than comparison operators for sorting). This can be done either by writing in a more C style, or by providing iterations to the standard algorithms that are initialised with a dynamic size.

[hlef]

Sounds like we want a different approach here. I'll close this one for now and come back with what we discussed.