freenode suffered a horrible accident, we're moving to Libera.Chat

The problem is that right now Libera.Chat does not have a web chat
interface, and no guarantee as to what its URLs are gonna be like
; although staff have said they're probably gonna stick to the same stack
as before so we might end up with very similar looking URLs.

For the time being, we have to get rid of the webchat URLs. They will be
missed a bit. Maybe.

Before anybody asks, yes, I am aware of the po comments in German
translation catalogues including a freenode IRC protocol URL. If I do
anything about it now, somebody will helpfully revert my changes during
a message catalogue merge (it happened some time ago). So, not touching
those until release time.

Also nobody cares about Travis anymore. It's dead cruft, just leave it
alone. (What on earth is that massive base64 string anyway?)

CC #5797

CONTRIBUTING.md

@@ -6,7 +6,7 @@ Wesnoth was built with the hard work of volunteers all over the world! Everyone
 
 The best place to get in touch with the development team is on our [official Discord community server](https://discord.gg/battleforwesnoth) or on the [Wesnoth forums](https://forums.wesnoth.org/).
 
-The Discord server is mirrored to freenode IRC, channels: [`#wesnoth`](https://webchat.freenode.net/#wesnoth) (general discussions), [`#wesnoth-umc-dev`](https://webchat.freenode.net/#wesnoth-umc-dev) (questions about creating add-ons), [`#wesnoth-dev`](https://webchat.freenode.net/#wesnoth-dev)  (development of wesnoth mainline).
+The Discord server is mirrored to [Libera.Chat IRC](https://libera.chat), channels: #wesnoth (general discussions), #wesnoth-umc-dev (questions about creating add-ons), #wesnoth-dev (development of wesnoth mainline).
 
 ## Art and Music
 

data/campaigns/tutorial/scenarios/01_Tutorial_part_1.cfg

@@ -4,7 +4,8 @@
     id=tutorial
     # po: Hello, translators! The tutorial is meant to be a bit funny at the start,
     # po: welcoming new players. Please keep the friendly fun feeling!
-    # po: If you have any questions, ask in the forums or in the #wesnoth-dev channel on the Freenode IRC network.
+    # po: If you have any questions, ask in the forums or, the #wesnoth-dev channel on irc.libera.chat,
+    # po: or https://discord.gg/battleforwesnoth.
     name= _ "Wesnoth Tutorial — Part I"
     map_file=01_Tutorial_part_1.map
     next_scenario=2_Tutorial

doc/doxygen/doxygen.cpp

@@ -311,8 +311,8 @@ When adding new features, keep in mind the project philosophy,
 which is that of
 <a href="https://wiki.wesnoth.org/WesnothPhilosophy">KISS</a>.
 
-The development team hangs out in the IRC channel
-<a href="https://webchat.freenode.net/?channels=wesnoth-dev">@#wesnoth-dev on irc.freenode.net</a>.
+The development team hangs out in the <a href="https://discord.gg/battleforwesnoth">official Wesnoth Discord server</a>,
+and in the IRC channel @#wesnoth-dev on irc.libera.chat.
 Feel free to join us and ask any questions you may have about our codebase!
 
 */

doc/manual/manual.txt

@@ -156,7 +156,7 @@ Preferences::
 Credits::
  Click this button for a list of major Wesnoth contributors. You
  will often be able to reach them in real time at
- irc.freenode.org:6667 on #wesnoth or at https://discord.gg/battleforwesnoth
+ irc.libera.chat:6667 on #wesnoth or at https://discord.gg/battleforwesnoth
 
 Quit::
  Click this button to close Wesnoth.