irc: restore away status and message when connecting to away ZNC (#1059)

[sim642]

This PR is a fix for #1059. When numeric 306 is received (from ZNC on connection when away), WHOIS is requested on own nick using irc redirection to get the away message from numeric 301. Properly set away message is necessary for away bar item to actually show anything.

This implementation is not perfect because every 306 is followed by a WHOIS, even when using /away manually. Visually there's no difference but there is the added overhead of a single WHOIS request. Maybe additional conditions should be in place to only do the WHOIS when the 306 isn't the result of manual away change.

Also I did not test with away-notify capability which maybe makes this WHOIS trickery unnecessary.

[chrisglass]

I can confirm this works with the following:

Versions:

• ZNC 1.7.1 (OpenBSD): IPv6: yes, SSL: yes, DNS: threads, charset: no, i18n: no, build: cmake
• Weechat built from this PR on Ubuntu 18.04 using:
  • sudo apt build-dep weechat
  • mkdir build
  • cd build
  • cmake ..
  • make
  • sudo make install

Steps to verify:

• Connect to an IRC server via ZNC
• set /away test
• Disconnect weechat from ZNC
• Reconnect weechat to ZNC

The away status "test" is restored when reconnecting.

[chrisglass]

Is there anything I can do to further help with this issue?

I'm happy to put time in to get this merged if needed (or money, or whatever) simply because that would mean not having to run a weechat compiled from a branch as my daily driver...

I'm not a big fan of +1 comments, so, sorry about that, but it's been a year+ so I feel it's not too frequent to be annoying. Apologies if it is.

[flashcode]

@chrisglass: I just need time to fully test this PR.
There are currently 57 PR pending, it takes time to test them before merging.