Add missing asyncio 3.7 top-level functions (#2320)

stdlib/3/asyncio/__init__.pyi

@@ -97,6 +97,20 @@ if sys.platform != 'win32':
         start_unix_server as start_unix_server,
     )
 
+if sys.version_info >= (3, 7):
+    from asyncio.events import (
+        get_running_loop as get_running_loop,
+    )
+    from asyncio.tasks import (
+        all_tasks as all_tasks,
+        create_task as create_task,
+        current_task as current_task,
+    )
+    from asyncio.runners import (
+        run as run,
+    )
+
+
 # TODO: It should be possible to instantiate these classes, but mypy
 # currently disallows this.
 # See https://github.com/python/mypy/issues/1843

stdlib/3/asyncio/events.pyi

@@ -223,3 +223,6 @@ def set_child_watcher(watcher: Any) -> None: ...  # TODO: unix_events.AbstractCh
 
 def _set_running_loop(loop: AbstractEventLoop) -> None: ...
 def _get_running_loop() -> AbstractEventLoop: ...
+
+if sys.version_info >= (3, 7):
+    def get_running_loop() -> AbstractEventLoop: ...

stdlib/3/asyncio/runners.pyi

@@ -0,0 +1,9 @@
+import sys
+
+
+if sys.version_info >= (3, 7):
+    from typing import Awaitable, TypeVar
+
+    _T = TypeVar('_T')
+
+    def run(main: Awaitable[_T], *, debug: bool = ...) -> _T: ...

stdlib/3/asyncio/tasks.pyi

@@ -1,8 +1,9 @@
+import concurrent.futures
+import sys
 from typing import (Any, TypeVar, Set, Dict, List, TextIO, Union, Tuple, Generic, Callable,
                     Coroutine, Generator, Iterable, Awaitable, overload, Sequence, Iterator,
                     Optional)
 from types import FrameType
-import concurrent.futures
 from .events import AbstractEventLoop
 from .futures import Future
 
@@ -70,3 +71,8 @@ class Task(Future[_T], Generic[_T]):
     def cancel(self) -> bool: ...
     def _step(self, value: Any = ..., exc: Exception = ...) -> None: ...
     def _wakeup(self, future: Future[Any]) -> None: ...
+
+if sys.version_info >= (3, 7):
+    def all_tasks(loop: Optional[AbstractEventLoop] = ...) -> Set[Task]: ...
+    def create_task(coro: Union[Generator[Any, None, _T], Awaitable[_T]]) -> Task: ...
+    def current_task(loop: Optional[AbstractEventLoop] = ...) -> Optional[Task]: ...