Fix a subtle decref bug that caused a GC assertion to fail in a debug

build (assert(gc->gc.gc_refs != 0) in visit_decref()).

Because OSSAudioError is a global, we must compensate (twice!) for
PyModule_AddObject()'s "helpful" decref of the object it adds.

Modules/ossaudiodev.c

@@ -938,6 +938,9 @@ initossaudiodev(void)
 
     OSSAudioError = PyErr_NewException("ossaudiodev.OSSAudioError", NULL, NULL);
     if (OSSAudioError) {
+	/* Each call to PyModule_AddObject decrefs it; compensate: */
+	Py_INCREF(OSSAudioError);
+	Py_INCREF(OSSAudioError);
         PyModule_AddObject(m, "error", OSSAudioError);
         PyModule_AddObject(m, "OSSAudioError", OSSAudioError);
     }