shmaddr is a pointer, so use NULL instead 0f

Per POSIX, we now only require <sys/msg.h>, <sys/sem.h>, or <sys/shm.h>

obvious .Pa fixes; found with mandocdb(8)

convert to new .Dd format;

typos;

reboot(2), sigaction(2): help and ok millert@

.Xr ipcs 1
.Xr ipcrm 1

grendel at zeitbombe dot org
some input millert
ok millert ian theo

Another round of man page cleanup, this time to remove more hard sentence
breaks and getting rid of short lines, making these files easier to work with.

Mostly punctuation fixes.

Typo fixes.

- change references to nil to null; tschroed@acm.org
- remove trailing spaces from end of lines
- add some .Dv
- change -1 to \-1, so `-' is taken as a negative sign
- other misc formatting fixes

add missing .El macros (which properly terminate .Bl macro lists)

add some .Dv and .Er, replace blank lines with .Pp

const a few more calls

fix mispelling of EACCES; bde

We run OpenBSD not NetBSD
From NetBSD:
Fix includes specified for shmctl(2)
Make xrefs consistent

Attempt at cleanup.

properly add them...