Add a note about alarm messages in live mode.
Decode the alarm bits somewhat further, mostly group them and mention the
main regions.

Obtained from "Vortrag INS Bevoelkerungswarnung Hannovermesse 2008.pdf" by
Mr. Karl Wenzelewski from DIN, with permission.

Note that this alarm system is currently not in use and that the decoding
is not complete. There were successful field tests but the encoding was
probably never formally finalized.