Added custom rasterizer vertex structure

 - Does not have unneccessary parameters
 - Removed interpolation of unneccessary parameters
 - Fixed clipping
 - Depht already calculated in the rasterizer
 - Pixel drawing functions get pointer to constant value

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
Reverted to 8 bit integer color (won't do HDR anyway)

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>
Replaced floatingpoint depth buffer with 24 bit integer

 - Rasterizer interpolates integer depth value
 - Depht buffer has integer type
 - No more floatingpoint calculations in pixel drawing functions

Signed-off-by: David Oberhollenzer <david.oberhollenzer@tele2.at>