Fix breakage due to __thread

Thread-local storage is not supported on all hosts.
Signed-off-by: NBlue Swirl <blauwirbel@gmail.com>

monitor.c

@@ -3229,7 +3229,7 @@ struct QemuErrorSink {
     QemuErrorSink *previous;
 };
 
-static __thread QemuErrorSink *qemu_error_sink;
+static QemuErrorSink *qemu_error_sink;
 
 void qemu_errors_to_file(FILE *fp)
 {