Add std support

[overdrivenpotato]

This can be done via a fork for now, but ideally we can upstream this to the official rust repo. Depends on #49

[MrAwesome]

Is there a checklist anywhere documenting what needs to be done for this and #49? I'm very interested in helping out.

[sajattack]

We're currently waiting on rust-lang/libc#1797 and then we need to implement something similar to https://github.com/rust-lang/rust/tree/master/src/libstd/sys/wasm

[to-mas-kral]

Hi :) rust-lang/libc#1797 is merged now. What exactly needs to be done ? (https://github.com/rust-lang/rust/tree/master/src/libstd/sys/wasm doesn't go anywhere).

[sajattack]

We need to implement a sys directory in libstd for psp, which we've started doing here: https://github.com/overdrivenpotato/rust/tree/psp_std/library/std/src/sys/psp We got a bit stuck with concurrency primitives, and there is a kanban board here https://github.com/overdrivenpotato/rust/projects/1