This is mainly to ease the usage of memory access functions, meaning
leaner access of memory with general resulution of memory accesses via
the MemoryIndex struct.
Previously, the displacement for a MemoryIndex was directly interpreted
and saved as a signed value.
Change this to the normal unsigned ImmediateOperand version to allow
for more flexible usage of this struct for general memoryaccess (future
commit) and just interpret the displacement member as signed, only when
being interpreted as such (memory access, display, ....
It's not possible to know if a word or byte is requested, or rather
it would be a pain to retrieve that information.
It is much easier to just read a full word and then discard the top
half, if just a byte is needed.
