bpo-30860: Consolidate stateful runtime globals. (#3397)

* group the (stateful) runtime globals into various topical structs
* consolidate the topical structs under a single top-level _PyRuntimeState struct
* add a check-c-globals.py script that helps identify runtime globals

Other globals are excluded (see globals.txt and check-c-globals.py).
diff --git a/Parser/myreadline.c b/Parser/myreadline.c
index 1b63f78..7fe04a9 100644
--- a/Parser/myreadline.c
+++ b/Parser/myreadline.c
@@ -10,6 +10,7 @@
 */
 
 #include "Python.h"
+#include "internal/pystate.h"
 #ifdef MS_WINDOWS
 #define WIN32_LEAN_AND_MEAN
 #include "windows.h"