- don't declare nonexistent function sleep().
- don't include <sys/errno.h> explicitly.
sleep() should be nuked some more, e.g., this man page should not be
named after a nonexistent function.
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.
