[ios] - fix iphone5s screensize on ios8.x runtime

As the title says. Also this PR replaces the outdated launchimages with plain black (appname agnostic).

This doesn't need buildtesting - it came out of the gotham 13.2-1 release which hit iphone5s users :) (fyi - will do 13.2-2 for cydia with this fix in aswell...).