PyErr_Occurred(): Use PyThreadState_GET(), which saves a tiny function call

in release builds.  Suggested by Martin v. Loewis.

I'm half tempted to macroize PyErr_Occurred too, as the whole thing could
collapse to just
     _PyThreadState_Current->curexc_type

Python/errors.c

@@ -75,7 +75,7 @@ PyErr_SetString(PyObject *exception, const char *string)
 PyObject *
 PyErr_Occurred(void)
 {
-	PyThreadState *tstate = PyThreadState_Get();
+	PyThreadState *tstate = PyThreadState_GET();
 
 	return tstate->curexc_type;
 }