Clean up and optimize section_delete().

At most generates two SQL queries instead of 102.
This and the memory usage could be cut even more, but
would result in inability to filter values before passing them
to the activity message or callback handlers.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5282 2fea6a4d-a838-0410-917b-93a53c48e9d2
Missing return.

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5283 2fea6a4d-a838-0410-917b-93a53c48e9d2