Simplify CPP expressions.
Simplify CPP expressions.

This simplification pass currently does:

- Bind/Bind simplification
- Call/Bind simplification
- Bind/0 simplification

As long as functions are appropriately saturated with arguments,
everything should just work. Weird issues with polymorphic functions
could still break things.

DaMSL/K3,DaMSL/K3,yliu120/K3