correct history of /dev/mem and /dev/kmem

The history section (added in CSRG) claimed both first appeared in v6.
Looking at the manuals in the TUHS archive, /dev/mem was in v1 and
/dev/kmem was intr

correct history of /dev/mem and /dev/kmem

The history section (added in CSRG) claimed both first appeared in v6.
Looking at the manuals in the TUHS archive, /dev/mem was in v1 and
/dev/kmem was introduced in v5.

ok jan@

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Adjust references for sysctl(3) to sysctl(2)

Update the documentation regarding /dev/mem and /dev/kmem;
Theo already clamped down on these devices last year.
Triggered by a question from Nan Xiao <xiaonan830818 at gmail dot com>.
OK deraadt@

convert to new .Dd format;

add manpages for physical and kernel virtual memory, plus onboard I/O

ok jmc@