Register allocation V2

This lays the groundwork for other on-the-fly optimisations,
like passing literals through in order to do const folding
in linear time, while compiling.

src/lib.rs

@@ -9,8 +9,10 @@ extern crate wasmparser;
 #[macro_use]
 extern crate failure_derive;
 extern crate dynasmrt;
+#[cfg(test)]
 #[macro_use]
 extern crate lazy_static;
+#[cfg(test)]
 #[macro_use]
 extern crate quickcheck;
 extern crate wabt;