When reporting errors for failing to open files, give error text
rather than errno number. Patch from Joey Hess <joey@kitenet.net> for
Debian bug 187251 from Mikael Hedin <micce@debian.org>.
This merges in all such remaining changes from the Linux port of the
NetBSD games, except in hunt (where substantial changes from OpenBSD
need to be looked at).
Some such changes were previously covered in PRs bin/6041, bin/6146,
bin/6148, bin/6150, bin/6151, bin/6580, bin/6660, bin/7993, bin/7994,
bin/8039, bin/8057 and bin/8093.