Add some constness to avoid some warnings.
Remove use register keyword.
Deal with missing/unneeded extern/prototypes.
Some minor type changes/casts to avoid warnings.
Reviewed by: md5
This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.
Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.