[WIP] Implement subroutine opcodes

Author: Peppece

eth/vm/rstack.py

@@ -27,7 +27,7 @@ class RStack():
     VM Return Stack
     """
 
-    __slots__ = ['values', '_append', '_pop_int', '__len__']
+    __slots__ = ['values', '_append', '_pop_typed', '__len__']
 
     def __init__(self) -> None:
         values: List[int] = []