builtins: int.__pow__ can take a modulo argument (#3192)

See:
https://docs.python.org/3/reference/datamodel.html#object.__pow__
https://docs.python.org/3/library/functions.html#pow

Author: bluetech

stdlib/2/__builtin__.pyi

@@ -168,7 +168,7 @@ class int:
     def __rtruediv__(self, x: int) -> float: ...
     def __rmod__(self, x: int) -> int: ...
     def __rdivmod__(self, x: int) -> Tuple[int, int]: ...
-    def __pow__(self, x: int) -> Any: ...  # Return type can be int or float, depending on x.
+    def __pow__(self, __x: int, __modulo: Optional[int] = ...) -> Any: ...  # Return type can be int or float, depending on x.
     def __rpow__(self, x: int) -> Any: ...
     def __and__(self, n: int) -> int: ...
     def __or__(self, n: int) -> int: ...

stdlib/2and3/builtins.pyi

@@ -168,7 +168,7 @@ class int:
     def __rtruediv__(self, x: int) -> float: ...
     def __rmod__(self, x: int) -> int: ...
     def __rdivmod__(self, x: int) -> Tuple[int, int]: ...
-    def __pow__(self, x: int) -> Any: ...  # Return type can be int or float, depending on x.
+    def __pow__(self, __x: int, __modulo: Optional[int] = ...) -> Any: ...  # Return type can be int or float, depending on x.
     def __rpow__(self, x: int) -> Any: ...
     def __and__(self, n: int) -> int: ...
     def __or__(self, n: int) -> int: ...