Fix bug in alter_areas() - the function for modifying the area file (areas.bbs)

in response to AreaFix requests: this function attempted to support a trailing
comment (beginning with a semicolon, but after any/all links) - but failed to
so correctly. Since, forever. So it's unlikely sysops actually added trailing
comments to their area file (or didn't provide AreaFix support to their
downlinks), but this "feature" should actually work now. I considered just
removing this support but decided to fix it instead, at least for now.