ptmalloc2 submodule not available

[binsky08]

The required ptmalloc2 submodule is not publicly accessible: https://github.tamu.edu/peiming/ptmalloc2
I'd love to try XRust myself and would appreciate if you could provide this dependency on GitHub :)

[cdstanford]

FYI, from Peiming Liu:

We do have a GitHub repo for the XRust, but it can no longer be compiled. The reason is that XRust is dependent on out dated Rust compiler, and many of the dependencies it relies on can not even be indexed by crates.io anymore…