Issue #19611: handle implicit parameters in inspect.signature

inspect.signature now reports the implicit ``.0`` parameters generated by
the compiler for comprehension and generator expression scopes as if they
were positional-only parameters called ``implicit0``.

Patch by Jelle Zijlstra.
diff --git a/Misc/ACKS b/Misc/ACKS
index ee67e27..7f289fb 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -1665,6 +1665,7 @@
 Cheng Zhang
 Kai Zhu
 Tarek Ziadé
+Jelle Zijlstra
 Gennadiy Zlobin
 Doug Zongker
 Peter Åstrand
diff --git a/Misc/NEWS b/Misc/NEWS
index 5a1d4d5..0dc317e 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -27,6 +27,11 @@
 Library
 -------
 
+- Issue #19611: :mod:`inspect` now reports the implicit ``.0`` parameters
+  generated by the compiler for comprehension and generator expression scopes
+  as if they were positional-only parameters called ``implicit0``.
+  Patch by Jelle Zijlstra.
+
 - Issue #26809: Add ``__all__`` to :mod:`string`.  Patch by Emanuel Barry.
 
 - Issue #26373: subprocess.Popen.communicate now correctly ignores