bpo-43356: Allow passing a signal number to interrupt_main() (GH-24755)

Also introduce a new C API ``PyErr_SetInterruptEx(int signum)``.
diff --git a/PC/python3dll.c b/PC/python3dll.c
index 3f87b70..027d4b1 100644
--- a/PC/python3dll.c
+++ b/PC/python3dll.c
@@ -209,6 +209,7 @@ EXPORT_FUNC(PyErr_SetFromWindowsErrWithFilename)
 EXPORT_FUNC(PyErr_SetImportError)
 EXPORT_FUNC(PyErr_SetImportErrorSubclass)
 EXPORT_FUNC(PyErr_SetInterrupt)
+EXPORT_FUNC(PyErr_SetInterruptEx)
 EXPORT_FUNC(PyErr_SetNone)
 EXPORT_FUNC(PyErr_SetObject)
 EXPORT_FUNC(PyErr_SetString)