SMF updated to version 1.1.21

[Ingar]

I patched the Simple Machines forum to the latest version in the 1.1.x branch,
hoping this will stop the flood of new spambots we've seen last month.
As we all know, admins need to keep software up-to-date as spammers like to
use known exploits in outdated versions. It's a pain, but such is life.

Please report any broken functionality here.

[Ingar]

Some spambots were still getting through.
I updated the registration question and activated E-mail confirmation on registration.