Bare-bones ptracing functionality

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 ;)

Should be merged together with syscall!36 (merged)