(bug 26690) Value of the 'Name of wiki' field is not retain after two subsequent...

(bug 26690) Value of the 'Name of wiki' field is not retain after two subsequent click on 'Continue' button. This has been a complaint since the beginning, that the installer "forgets" $wgSitename.

The original intention, as I saw it, was to encourage people from choosing 'MediaWiki' as the name of their wiki. Just hardcode it, I don't think we're changing the name anytime soon.