Upgrading to pxt 3.5.4 (#367)

* pxt/common updates

* added game lib

* removing gamelib

libs/core/png.cpp

@@ -28,7 +28,7 @@ static uint32_t swap(uint32_t num) {
 
 /** Decompresses a 1-bit gray scale PNG image to image format. */
 //%
-Image unpackPNG(Buffer png) {
+Image_ unpackPNG(Buffer png) {
     if (!png) {
         DMESG("PNG: Missing image");
         return NULL;

libs/core/screen.cpp

@@ -45,10 +45,10 @@ static void bitBufferToFrameBuffer(uint8_t *bitBuffer, uint8_t *fb) {
 }
 
 static uint8_t *mappedFrameBuffer;
-static Image lastImg;
+static Image_ lastImg;
 
 //%
-void updateScreen(Image img) {
+void updateScreen(Image_ img) {
     if (img && img != lastImg) {
         decrRC(lastImg);
         incrRC(img);