Motivation / Problem

#9017 gave a review comment that the debug statements in the ListenProc is a bit wonky. As a good citizen, I don't just fix the line I touched, but I went through all of them in both listen() and connect().

Description

I did a few things:

• All errors now show the OS error too; otherwise debugging problems can be hard.
• I bumped fatal errors to level 0, so the user actually sees what part failed.
• I removed many of the "tcp" and "ipv4" prefixes; they are rarely relevant for the error happening.
• I often removed the address from the error. For example, if socket() fails, it is not really important to what you were trying to listen(). The fact that we cannot do a simple socket() really is a big issue. Only if bind() fails, it is worth mentioning what we were trying to binding to.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker