Use unrealircd with proxy protocol support

[daurnimator]

Swap over to buildling unrealircd ourselves with the patch for PROXY support.

Currently doesn't work, as PROXY support doesn't play well with SSL (reported at https://bugs.unrealircd.org/view.php?id=5306#c20727)
I tried to work around it by having the DO load balancer terminate SSL; but DO only support HTTP traffic.

[daurnimator]

13:13:44 | | But essentially the issue is that IRC servers require that the source IP is the end user's source IP, not that of a load balancer
13:14:10 | | so options are: 1. don't use a load balancer (which DO doesn't allow). or 2. fake the source IP
13:14:55 | | I wasted days trying to trick DO into 1. but it just doesn't work
13:15:07 | | so then we started chasing 2. via using an envoy sidecar
13:15:29 | | but the dev/test cycle is long and error messages don't tell you much
13:15:38 | | so its hours and hours of guessing and trial and error