Highlight vc_dispmanx_snapshot() failure and link to bug trackers to …

…how to recover. raspberrypi/userland#461 #28

gpu.cpp

@@ -123,7 +123,8 @@ bool SnapshotFramebuffer(uint16_t *destination)
   int failed = vc_dispmanx_snapshot(display, screen_resource, (DISPMANX_TRANSFORM_T)0);
   if (failed)
   {
-    printf("vc_dispmanx_snapshot() failed with return code %d!\n", failed);
+    // We cannot do much better here (or do not know what to do), it looks like if vc_dispmanx_snapshot() fails once, it will crash if attempted to be called again, and it will not recover. We can only terminate here. Sad :/
+    printf("vc_dispmanx_snapshot() failed with return code %d! If this appears related to a change in HDMI/display resolution, see https://github.com/juj/fbcp-ili9341/issues/28 and https://github.com/raspberrypi/userland/issues/461 (try setting fbcp-ili9341 up as an infinitely restarting system service to recover)\n", failed);
     MarkProgramQuitting();
     return false;
   }