Issue #24619: New approach for tokenizing async/await.

This commit fixes how one-line async-defs and defs are tracked
by tokenizer.  It allows to correctly parse invalid code such
as:

>>> async def f():
...     def g(): pass
...     async = 10

and valid code such as:

>>> async def f():
...     async def g(): pass
...     await z

As a consequence, is is now possible to have one-line
'async def foo(): await ..' functions:

>>> async def foo(): return await bar()

1 files changed, 1 insertions, 4 deletions

diff --git a/Lib/test/test_grammar.py b/Lib/test/test_grammar.py
index 2af7390..ca6b5d0 100644
--- a/Lib/test/test_grammar.py
+++ b/Lib/test/test_grammar.py
@@ -1051,10 +1051,7 @@ class GrammarTests(unittest.TestCase):
 
         async def test():
             def sum():
-                async = 1
-                await = 41
-                return async + await
-
+                pass
             if 1:
                 await someobj()