Writing a simple Core evaluator, having trouble with name lookups

[Christopher Done]

I think what Csaba means is that we can have e.g.

* GHC invocation 1
  * ghc-prim:
    * MyModule.foo has Unique 123
    * OtherModule.bar has Unique 124
* GHC invocation 2
  * base:
    * MyMod.mu has Unique 123
    * OtherMod.zot has Unique 124

For a unique reference then, we just need:

* ghc-prim:MyMobile.foo+123
* ghc-prim:OtherModule.bar+124
* base:MyMod.mu+123
* base:OtherMod.zot+124

For any local lookup this is reliable. If the lookup fails, a lookup
without the Unique works for cross-module lookups.