[commit] feDisplacementMap, feImage filter region fix

[Vincent Hardy <vi...@eng.sun.com>]

I commited the following:

a. feDisplacementMap and related test case (in samples/tests). We pass
   the BE for this filter.

b. Fixes in the feImage bridge. I implemented the default filter region
   to be the one of the filter chain (not the source) as per the spec.
   I also add the additional transforms needed to implement the behavior
   on raster and non raster content. Actually, I do not believe I have
   done a complete job for the SVG case because feImage is supposed 
   to implement the same behavior as <use> in that case. Also, I think 
   we need to add the processing of the transform attribute.
   I updated the feImage, feComposite and feMerge test cases to specify
   the filter chain region so that the -10%, -10%, 120%, 120% default
   does not kick in.

c. Update to thumbnails.svg so that it now includes the feImage,
feComposite
   and feMerge test cases.

V.