fix alignment handling when reading images
fix alignment handling when reading images

The code was confusing sizes in pixels and bytes when doing the
alignment calculations. Workaround it for now even if it will only
work with 16bpp formats :-/

hyperair/libgpod,hyperair/libgpod,neuschaefer/libgpod,neuschaefer/libgpod,hyperair/libgpod,hyperair/libgpod,neuschaefer/libgpod,neuschaefer/libgpod,neuschaefer/libgpod,hyperair/libgpod