More RFC (3977) conformance

Some of the NNTP commands (e.g. LIST) aren't supposed to change the "currently
selected newsgroup". Had to use a different variable name (e.g. mb versus
msgbase) since these message base variables share the function scope).

GROUP and LISTGROUP commands are supposed to set the "current article number"
to the first article in the group. We weren't doing this.

The HEAD, BODY, STAT, and ARTICLE commands aren't *required* to have arguments
and yet, we required they had at least one argument (an article number). Now
fixed.

Enabled "strict mode" even though that didn't catch the colliding 'msgbase'
variable definitions.

Incremented the revision to 1.2