The multi-level APIs still don't check anything regarding level sizes
and order since for example *.ico has no restrictions at all. But the
rest (like non-zero size) is a restriction for all file formats I'm
aware of.
TgaImageConverter test had to be adapted, I expect a lot of breakages in
plugins tests as well. But user code should be fine I think. Also
reduced the rather excessive dimensions in AbstractImageConverterTest,
since the allocation requirement now made the default Emscripten heap
OOM.
Vladimír Vondruš