Add support for muzi-base

src/graphics/Screen.h

@@ -249,6 +249,8 @@ class Screen : public concurrency::OSThread
 
     bool isOverlayBannerShowing();
 
+    bool isScreenOn() { return screenOn; }
+
     // Stores the last 4 of our hardware ID, to make finding the device for pairing easier
     // FIXME: Needs refactoring and getMacAddr needs to be moved to a utility class
     char ourId[5];