Switch to RGBx pixel format

This is what the browser wants so it avoids having to spend time
converting everything. Unfortunately it usually means the server instead
needs to convert it for us, but we assume it has more power than we do.

tests/test.copyrect.js

@@ -38,7 +38,7 @@ describe('CopyRect Decoder', function () {
     it('should handle the CopyRect encoding', function () {
         // seed some initial data to copy
         display.fillRect(0, 0, 4, 4, [ 0x11, 0x22, 0x33 ]);
-        display.fillRect(0, 0, 2, 2, [ 0xff, 0x00, 0x00 ]);
+        display.fillRect(0, 0, 2, 2, [ 0x00, 0x00, 0xff ]);
         display.fillRect(2, 0, 2, 2, [ 0x00, 0xff, 0x00 ]);
 
         testDecodeRect(decoder, 0, 2, 2, 2,