[TUHS] 4.1c bsd ptrace man entry

[Doug McIlroy]

Ptrace was short-lived at Research, appearing in 6th through 8th editions.
/proc was introduced in the 8th. Norman axed it in the 9th.

Norman wrote:
 nobody wanted
to update adb and sdb, which were big messes inside.  So I did
...
Once I'd done that and shipped the new adb and sdb binaries to
all our machines, I removed the ptrace call from the kernel.

doug