Qualshrink: remove the global constants generated by GHC `Literal` values

The `Literal` were converted to `int` constants that polluted the global namespace, 
making solving unnecessarily slow, due to bogus instantiations. Worse, the damn 
things aren't even needed!

Data/ByteString.hs now runs in 5mins or so (with the SMTLIB2 Z3 bindings, 
probably even faster if we can link against z3 v4 api).

co-request with ucsd-progsys/liquid-fixpoint#16