Since even a very basic ptrace can be nice to have, I thought I would split
the, perhaps rather big, ptrace project up in multiple PRs to make as few
changes as necessary in each. This PR contains the initial registry modifying
bits and only a very basic security measure. Letting this out to the community
should be good for spotting bugs and maybe getting some hype ;)

This reverts merge request !103

I'm guessing it's some issue after a rebase or something...

Most of this was generated by the absolutely extraordinary `cargo fix`
subcommand. There were still 2 errors and a few warnings to patch up,
but compared to the normal 600+ errors, I'd say the fixer did a damn
good job! I'm also amazed that I could still start the VM after this,
I half expected some kinds of runtime failure...

Fix memory leaks in exec
Remove warnings

Update debugging code

Implement interrupt on signal in pipe: