fix the return values of getChunkSlices so when an extra tall box is requested, the offset point and slices line up properly
fix the return values of getChunkSlices so when an extra tall box is requested, the offset point and slices line up properly

codewarrior0/pymclevel,mcedit/pymclevel,mcedit/pymclevel,arruda/pymclevel,ahh2131/mchisel,arruda/pymclevel,codewarrior0/pymclevel,ahh2131/mchisel