[PATCH] Let gcore use ptrace interface rather than the procfs

This patch allows gcore to use the ptrace interface rather than procfs:
http://www.freebsd.org/~attilio/Sandvine/STABLE_8/gcore/gcore.diff

The main visible effect of that is that gcore can now work on a
per-thread scope, offering a granularity procfs can't reach.
A downside, though, is that the process to be targeted is going to be
stopped with ptrace.
This patch has been contributed back by Sandvine Incorporated.
Comments, reviews and testing are welcome.

Thanks,
Attilio


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