This helper to determine alignment for hardware blitting is now in
system/helpers.h, where it does not really belong. Put it into the
framebuffer class instead. Framebuffers that don't need it will just
get a dummy function, the cs_hd2 framebuffer gets the real thing.
Also add a bool function that indicates the need for alignment.
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.
