Remove unused rleEnd field.
Convert RGBImageReader::getRow to take unsigned coordinates

Logically, the coordinates have to be unsigned and using unsigned type
avoids promotion of unsigned to signed in fread.
Remove dead code

At the point where slices is compared to 6 it can be either 30 or
7 (30/4), both of which are greater than 6.
Merge branch 'master' into qt

Conflicts:
	src/gl/texture.cpp