* include <mips/locore.h> where callbacks into locore are made, to get
prototypes in scope. Cast calls appropriately.
* include <mips/cpuregs.h>, not the old Sprite-derived <machine/machConst.h>.
machConst.h is deprecated.
* dk_establish() must return void, not int.
* Add cast to hardclock when it's used directly as an interrupt handler.
* Add a null-interrupt-establish function, to avoid int vs void lint
in pica/dev/dma.c.
* fix include in pica/include/pccons.h to work with "standard"
kernel-compile include path.