[WIP] Build runtime with colonyjit-interpreter.

This PR replaces #351.

Merges "colonyjit" branch of LuaJIT into master. Building currently requires the following invocation:

```
make HOST_CFLAGS="-DLUAJIT_COLONY -g" TARGET_CFLAGS="-DLUAJIT_COLONY -ggdb" || true
```

Steps until merge:

* [x] Get all tests passing when building with LuaJIT.
* [ ] Check that firmware builds work with LuaJIT.