another pair of files which relied on mbuf.h for pool.h; should be the last,

another pair of files which relied on mbuf.h for pool.h; should be the last,
as the kernel now compiles w/o ``#include <sys/pool.h>'' in mbuf.h; removing
that line, though, is for another day, as a userland program (systat, IIRC)
fails to build without it there.

ok krw@