Fix regression after c8d1df9ac987

(PPC buildbot)

Include/genobject.h

@@ -18,7 +18,7 @@ typedef struct {
     struct _frame *gi_frame;
 
     /* True if generator is being executed. */
-    int gi_running;
+    char gi_running;
     
     /* The code object backing the generator */
     PyObject *gi_code;