included twice by lprint.c, which included both finger.h and extern.h.
finger.h, in turn, includes extern.h. The redundant include of extern.h
was removed from lprint.c, as part of this change, but the include guards
were added anyway out of spite.
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
