Mobile: icons Ocsigen on iOS -> black background.

[dannywillems]

[dannywillems]

The black background comes from the transparent background of the icon (assets/images/icon.png). The problem can be solved by adding a white background which is did in Makefile.mobile with convert -background white but it doesn't seem to be enough.

If I manually set a white background to the PNG file, it's working but we have not a transparent background on Android.