PLT Redex definition of STG as per fast curry paper

[Edward Z. Yang]

For those of you who aren't following the commit list, I've just pushed
a PLT Redex <http://redex.racket-lang.org/> definition for an STG-like
language as was defined in the fast curry paper.  This language is *not*
STG.  The hope is that this will be a good starting point for actually
formalizing STG as it exists today.  I've included a hefty comment block
at the top of the development summarizing ways in which this could be
improved.  Take a look if you're interested!

Cheers,
Edward