bpo-42246: Partial implementation of PEP 626. (GH-23113)

* Implement new line number table format, as defined in PEP 626.
diff --git a/Lib/test/test_opcodes.py b/Lib/test/test_opcodes.py
index 1152eb6..e510364 100644
--- a/Lib/test/test_opcodes.py
+++ b/Lib/test/test_opcodes.py
@@ -27,7 +27,7 @@ def test_setup_annotations_line(self):
             with open(ann_module.__file__) as f:
                 txt = f.read()
             co = compile(txt, ann_module.__file__, 'exec')
-            self.assertEqual(co.co_firstlineno, 3)
+            self.assertEqual(co.co_firstlineno, 1)
         except OSError:
             pass