Added DumpRenderTree support with CMake.  Also:
+ Made using CF optional.
+ Fixed bug in ImageDiff creating difference image.
+ Fixed bug in PixelDumpSupportCairo.cpp - images are expected to be 32bpp,
  not 24bpp.
+ Changed DRT file includes to be full path.
Fixed bug preventing animations from running.

Animations were broken for ports not using ACCELERATED_COMPOSITING with
webkit.org commit 147792 <http://trac.webkit.org/changeset/147792>.