Perform build and magnum tuning

Building o//third_party/python now takes 5 seconds on my PC

This change works towards modifying Python to use runtime dispatching
when appropriate. For example, when loading the magnums in the socket
module, it's a good idea to check if the magnum is zero, because that
means the local system platform doesn't support it.

third_party/python/Include/pythread.h

@@ -1,14 +1,11 @@
-
 #ifndef Py_PYTHREAD_H
 #define Py_PYTHREAD_H
+COSMOPOLITAN_C_START_
+/* clang-format off */
 
 typedef void *PyThread_type_lock;
 typedef void *PyThread_type_sema;
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 /* Return status codes for Python lock acquisition.  Chosen for maximum
  * backwards compatibility, ie failure -> 0, success -> 1.  */
 typedef enum PyLockStatus {
@@ -83,8 +80,5 @@ PyAPI_FUNC(void) PyThread_delete_key_value(int key);
 /* Cleanup after a fork */
 PyAPI_FUNC(void) PyThread_ReInitTLS(void);
 
-#ifdef __cplusplus
-}
-#endif
-
+COSMOPOLITAN_C_END_
 #endif /* !Py_PYTHREAD_H */