Added comments to create transparent framebuffer

Comments to create transparent framebuffer on RPI,
when activate you see though full screen window the console below!

src/core.c

@@ -1836,8 +1836,8 @@ static void InitGraphicsDevice(int width, int height)
         EGL_RED_SIZE, 8,            // RED color bit depth (alternative: 5)
         EGL_GREEN_SIZE, 8,          // GREEN color bit depth (alternative: 6)
         EGL_BLUE_SIZE, 8,           // BLUE color bit depth (alternative: 5)
-        //EGL_ALPHA_SIZE, 8,        // ALPHA bit depth
-        //EGL_TRANSPARENT_TYPE, EGL_TRANSPARENT_RGB, // Request transparent framebuffer
+        //EGL_ALPHA_SIZE, 8,        // ALPHA bit depth (required for transparent framebuffer)
+        //EGL_TRANSPARENT_TYPE, EGL_NONE, // Request transparent framebuffer (EGL_TRANSPARENT_RGB does not work on RPI)
         EGL_DEPTH_SIZE, 16,         // Depth buffer size (Required to use Depth testing!)
         //EGL_STENCIL_SIZE, 8,      // Stencil buffer size
         EGL_SAMPLE_BUFFERS, sampleBuffer,    // Activate MSAA
@@ -1912,7 +1912,7 @@ static void InitGraphicsDevice(int width, int height)
 
     VC_DISPMANX_ALPHA_T alpha;
     alpha.flags = DISPMANX_FLAGS_ALPHA_FIXED_ALL_PIXELS;
-    alpha.opacity = 255;
+    alpha.opacity = 255;    // Set transparency level for framebuffer, requires EGLAttrib: EGL_TRANSPARENT_TYPE
     alpha.mask = 0;
 
     dispmanDisplay = vc_dispmanx_display_open(0);   // LCD