Tweak ZXBox colours: 1) 'Bright' black is the same as normal black on a real Spectrum, so make it so here too. 2) Use more accurate RGB values in the 16bpp driver (taken from the FUSE emulator). 3) Remove some confusing duplicate definitions.
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@17638 a1c6a512-1295-4272-9138-f99709370657