DFB Port: Import code from main DirectFB webkit repository.

This basically copies DirectFB specific code parts from webkitdfb-124228.
The specific commit id is fcfe99776148c410dbf1513972f069922d3f9eb1.

Both ilixi and LiTE ports should be working. Rendering via cairo is
supported but video support needs to be disabled in this case. Currently
StillImageDFB (required by video support) does not work with Cairo.

Signed-off-by: Peter Tworek <tworaz666@gmail.com>