start modularizing framebuffer acceleration architecture

This is just copied framebuffer.{h,cpp} => fb_generic.{h,cpp}
The idea is to implement CFrameBuffer as generic framebuffer class that
does work on almost every hardware without acceleration and / or
hardware dependencies.
CFbAccel will be a derived class (and different on many architectures)
which implements the accelerated functions.
This does not yet compile, verbatim copies to track development history.

src/driver/framebuffer.h

@@ -21,6 +21,8 @@
 	Boston, MA  02110-1301, USA.
 */
 
+#include "fb_generic.h"
+#if 0
 
 #ifndef __framebuffer__
 #define __framebuffer__
@@ -330,3 +332,4 @@ class CFrameBuffer : public sigc::trackable
 };
 
 #endif
+#endif