first pass at function prototypes with cdefs.h

first pass at function prototypes with cdefs.h
protect include files included by other include files with #ifndef _NAME_H_

SCCS-vsn: sys/sys/signal.h 7.15
SCCS-vsn: sys/sys/ttychars.h 7.5
SCCS-vsn: sys/sys/tablet.h 7.4
SCCS-vsn: sys/sys/vcmd.h 7.3
SCCS-vsn: sys/sys/namei.h 7.12
SCCS-vsn: sys/sys/types.h 7.13
SCCS-vsn: sys/sys/wait.h 7.14
SCCS-vsn: sys/sys/dir.h 7.3
SCCS-vsn: sys/sys/dmap.h 7.2
SCCS-vsn: sys/sys/stat.h 7.9
SCCS-vsn: sys/sys/uio.h 7.6
SCCS-vsn: sys/sys/times.h 7.5
SCCS-vsn: sys/sys/ucred.h 7.5
SCCS-vsn: sys/sys/ipc.h 7.2
SCCS-vsn: sys/sys/cdefs.h 7.4
SCCS-vsn: sys/sys/ptrace.h 7.2
SCCS-vsn: sys/sys/time.h 7.5
SCCS-vsn: sys/sys/resource.h 7.4
SCCS-vsn: sys/sys/exec.h 7.4
SCCS-vsn: sys/sys/unistd.h 5.9
SCCS-vsn: sys/sys/ioctl.h 7.13
SCCS-vsn: sys/sys/shm.h 7.2
SCCS-vsn: sys/sys/malloc.h 7.22
SCCS-vsn: sys/sys/ttydev.h 7.7
SCCS-vsn: sys/sys/sysctl.h 7.5
SCCS-vsn: sys/sys/fcntl.h 5.10
SCCS-vsn: sys/sys/termios.h 7.20
SCCS-vsn: sys/sys/ttydefaults.h 7.8
SCCS-vsn: sys/sys/ioctl_compat.h 7.4
SCCS-vsn: sys/sys/queue.h 7.2
SCCS-vsn: sys/sys/disklabel.h 7.15
SCCS-vsn: sys/sys/filedesc.h 7.2
SCCS-vsn: include/fstab.h 5.11
SCCS-vsn: include/grp.h 5.3
SCCS-vsn: include/pwd.h 5.6
SCCS-vsn: include/setjmp.h 5.3
SCCS-vsn: include/sgtty.h 5.1
SCCS-vsn: include/ttyent.h 5.6
SCCS-vsn: include/string.h 5.7
SCCS-vsn: include/math.h 5.1
SCCS-vsn: include/regexp.h 5.1
SCCS-vsn: include/nlist.h 5.5
SCCS-vsn: include/time.h 5.9
SCCS-vsn: include/utime.h 5.2
SCCS-vsn: include/dirent.h 5.16