* Add Atom and Literal base classes to CDSL Ast. Change substitution() and copy() on Def/Apply/Rtl to support substituting Var->Union[Var, Literal]. Check in Apply() constructor kinds of passed in Literals respect instruction signature
* Change verify_semantics to check all possible instantiations of enumerated immediates (needed to descrive icmp). Add all bitvector comparison primitives and bvite; Change set_semantics to optionally accept XForms; Add semantics for icmp; Fix typing errors in semantics/{smtlib, elaborate, __init__}.py after the change of VarMap->VarAtomMap
* Forgot macros.py
* Nit obscured by testing with mypy enabled present.
* Typo
