Report the correct file on error
Add support for longer config lines

With the introduction of CipherList we could have longer config lines.
Handle up to 1024 bytes and warn if the line will be truncated.
platformtest.sh: Detect clang compilers
ngIRCd Release 21~rc2
Debian: Fix default "HelpFile" file name in ngircd.conf

The "full" package variants must use "/usr/share/doc/ngircd-full/Commands.txt"
and "/usr/share/doc/ngircd-full-dbg/Commands.txt" respectively.
Debian: Fix sed(1) rules adjusting "ngircd-full" package

Error introduced by last commit :-/