bpo-32351: Use fastpath in asyncio.sleep if delay<0 (#4908)

* Use fastpath in asyncio.sleep if delay<0

* Add NEWS entry
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index cdb483a..275141c 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -503,7 +503,7 @@
 
 async def sleep(delay, result=None, *, loop=None):
     """Coroutine that completes after a given time (in seconds)."""
-    if delay == 0:
+    if delay <= 0:
         await __sleep0()
         return result
 
diff --git a/Misc/NEWS.d/next/Library/2017-12-17-14-23-23.bpo-32351.95fh2K.rst b/Misc/NEWS.d/next/Library/2017-12-17-14-23-23.bpo-32351.95fh2K.rst
new file mode 100644
index 0000000..56f52d2
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-12-17-14-23-23.bpo-32351.95fh2K.rst
@@ -0,0 +1 @@
+Use fastpath in asyncio.sleep if delay<0 (2x boost)