Move string guard into the common superclass.
Specialisations can also be slow path.
Move short name to correct node.
executeGeneric is already there really as execute.
Remove redundancy in some BigInteger comparisons.
Value in return exception should be final to help the PE.
Remove redundant super call.
Add very important final modifier in constant node.
executeVoid should live in LuaNode so we can execute any node and discard the result.
...which allows us to simplify statement.
We almost certainly don't want to pass nodes into the object graph.
Move some execute methods down into LuaNode.
Defensive programming: protect the runtime with neverPartOfCompilation.