move _heapq into 2and3/

builtins/2and3/_heapq.pyi

@@ -0,0 +1,15 @@
+"""Stub file for the '_heapq' module."""
+
+from typing import TypeVar, List
+
+_T = TypeVar("_T")
+
+def heapify(heap: List[_T]) -> None: ...
+def heappop(heap: List[_T]) -> _T:
+    raise IndexError()  # if list is empty
+def heappush(heap: List[_T], item: _T) -> None: ...
+def heappushpop(heap: List[_T], item: _T) -> _T: ...
+def heapreplace(heap: List[_T], item: _T) -> _T:
+    raise IndexError()  # if list is empty
+def nlargest(a: int, b: List[_T]) -> List[_T]: ...
+def nsmallest(a: int, b: List[_T]) -> List[_T]: ...