This adds a few smoke tests associated with libnative tasks (not much code to
test here anyway), and cleans up the entry points a little bit to be a little
more like libgreen.
The I/O code doesn't need much testing because that's all tested in libstd (with
the iotest! macro).
This commit introduces a new crate called "native" which will be the crate that
implements the 1:1 runtime of rust. This currently entails having an
implementation of std::rt::Runtime inside of libnative as well as moving all of
the native I/O implementations to libnative.
The current snag is that the start lang item must currently be defined in
libnative in order to start running, but this will change in the future.
Cool fact about this crate, there are no extra features that are enabled.
Note that this commit does not include any makefile support necessary for
building libnative, that's all coming in a later commit.
