check_station_category: filtering changes

The option "-special noinwork" is gone and the triggered filtering now
done by default, as all users of check_station_category in
data/Makefile were setting this option anyway.

Additionally, stations explitely marked as "disused" are now also
exempt from checks (this is needed for the special case Bergholz,
which is disused though there are active railway lines touching this
station).
data update (systematic corrections rbahn/rbahnhof)
route-pdf.t: fixed comment

Comment about unsupported utf-8 was only partially true: the
Cairo+Pango backend can deal with more scripts than PDF::Create.
strassen-sort.t: fixed encoding

bbd without declared encoding is latin1.
minor encoding issue in Pod
English comments
minor encoding issue in Pod
psgi: simplified
psgi: added some missing cgis (bbbikeleaflet etc.)
data update (mainly completion of Ahrensfelde)