I have now the following:
$wgScriptPath = "/+";
$wgArticlePath = "/$1";
with this in Apache:
Alias /= /home/pub/wiki
Alias /+ /var/lib/mediawiki
Alias / /var/lib/mediawiki/index.php/
and local DNS giving an IP address for hostname "wiki", and it has
been working now, with URLs like:
http://wiki/Main_Page
Yes, I know this means I cannot make an article with a name beginning with "+".