Re: [sr-dev] [kamailio/kamailio] Proxy Protocol support (#1757)

I seem to have made some good progress:

``` 10(20) INFO: {1 1 INVITE 6f350846ab60b1d60295d17268df1605@0.0.0.0} <script>: $si:$sp==35.156.191.128:42759, $Ri:$Rp==100.118.0.3:5060, $RAi:$RAp==staging-sip.dixa.io:5060 ```

`$si` and `$sp` are correct, and refer to the client details outside of the ELB. However, for some reason, `$Ri` and `$Rp` still refers to the bind-address, even though I do override the `dst` parts of the code. There's probably something I'm missing.

I'll submit the PR for review in a bit. @miconda Do you prefer that I squash all commits into a single one, or just clean up the commits into logical chunks?