Fix loading of images with multiple segments
Fix loading of images with multiple segments

For example: a recent Vivide image.
Bert seems to have fixed this in SqueakJS, so this
is an appropriate fix for RSqueak.
bridgeSpan appears to be zero on macOS/Linux, a
bridgeSpanMagicHeader does not seem to exist.

HPI-SWA-Lab/RSqueak,HPI-SWA-Lab/RSqueak,HPI-SWA-Lab/RSqueak,HPI-SWA-Lab/RSqueak