functions and signed/unsigned mismatch.

This will of course change if some of the unused functions
suddenly get used...

BCM5805 and BCM5820 units. So far I've merely taken a skim over the code
and changed a few things from their original contributed source
(de-shadowing variables, removing variables from the header, and
re-constifying some functions to remove warnings). If this gives
compilation problems on any system, please let me know. We will hopefully
know for sure whether this actually functions on a system with the relevant
hardware in a day or two.  :-)