M0 single deref

[Nathan Brown]

Hey m0 folks,

I finally got back to working on m0 and have managed to revert the
double deref change I made and still pass all tests. I did this by
changing the way that constants are stored in the c implementation. I
also fixed a few work-arounds in the c implementation. Now the c and
perl implementations both pass the full test suite.

Check it out if you like:
https://github.com/nbrown/parrot/tree/m0-c-single-deref/

-Nate