Loading a tiff image appears to trash the stack when
using the latest version of tifflib (3.7.0).
This is due to the fact that uint16's are passed into
libtiff's TIFFGetField() method, which is probably
assuming a 32 bit integer. Changing the two occurances
of uint16 to unit32 at the top of iLoadTiffInternal() (in
il_tiff.c) fixes the problem.