updated dmtcp major versions

The default [dmtcp](http://dmtcp.sourceforge.net) should really be updated to a more recent version, as it is now a major version behind (and more). I'm a nix newbie, but I needed to use this soon so it seemed like a good change to test out nix-build. So there are a few possible issues:

* My new `--replace` commands may or may not be working correctly. Without these, a python expression trying to access `$USER`  (e.g. `os.environ['USER']`) fails; it seems like `USER` is not being set correctly in the build environment. I attempted to hardcode it to the first build user for now (I guess this would work if it is possible to disable parallel builds). However, I have not checked that this works correctly because specifying `nix-build -A -K dmtcp` does not seem to leave the directory around, even though it now fails much later in the check phase.

* Five out of forty checks will still fail if `doCheck = true`. I haven't investigated these yet, but dmtcp seems to work well enough in general. I will try to investigate these more. Part of the problem could be I'm running in virtualbox for the moment.