Fix the systemd-conditional code

By using SYSTEMD_FOUND instead of SYSTEMDDAEMON_FOUND, where I forgot to
rename it…

Remove an unused parameter

Include the IRC hostname in the IRC RECEIVING and SENDING debug messages

fix #2715

Forge link uses https

Add a reload add-hoc command

Update the CHANGELOG and INSTALL files, mentioning c-ares

Add the FindCARES cmake module

Implement async DNS resolution using c-ares

fix #2533

Fix typo

Use a timer to try reconnecting to the XMPP server only each 2 seconds

When the connection is lost, immediately try to reconnect, then try to
reconnect every 2 seconds.  This is much better than the previous “Try to
re-connect as fast as possible”.

Remove the XmppComponent::last_auth bool that was never used anywhere

Properly display [DEBUG] on debug lines, instead of [ERROR]

Fix “connections” typo

Fix “cleanely” typo

Add a tl;dr section in the INSTALL file

Add a missing #include for sockaddr_in6

Fix the include guard of revstr.hpp

Document the new affiliation/role stuff, and update changelog

Change IRC modes when receiving an affiliation/role change request

fix #2946

Remove a recent debug line that should not be there