adapt to kauth, and while i'm here, fix typos. inspired by yamt@, thanks!
adapt to kauth, pointed out by yamt@, thanks!

the logic i used here is that hp-ux presumably takes cr_groups[0] as the
euid - see the diff. this should be tested (do people use it anyway?)
zap unused var
need struct proc.
make build.sh tools work. from matt.
sync with head - hopefully this will work
sync with head.
sync with head.
oops - *really* sync to head this time.
sync with head.
sync with head.
sync with head.
sync with head.
sync with head.
re-add kern_auth.c and kauth.h lost in commit storm
install kauth.h, from cube, thanks!
remove the (now unused) struct ucred * casts for NOCRED/FSCRED.
adapt to kauth...
include kauth.h
add kauth.h and kauth.9, noted by cube, thanks!