-Fix: ComposeColourXXX could work a tiny bit faster when using 256, not 255 as value to divide with; downside is that it can give alpha errors (frosch)
-Codechange: added CopyImageToBuffer, which produces a readable buffer for screenshots
-Fix: 32bpp-anim now holds animation on transparent objects to avoid strange graphical effects
-Fix: 32bpp-anim now works correct on mouse-movement (it holds the palette animation correctly)
-Codechange: introduced a hierachy of blitters to avoid a lot of code duplication
Note: this allows much easier adding other types of video-drivers, like OpenGL