Bug 832155: Move SVGFEDistantLightElement to its own file r=Ms2ger

--HG--
rename : content/svg/content/src/nsSVGFilters.cpp => content/svg/content/src/SVGFEDistantLightElement.cpp
rename : content/svg/content/src/nsSVGFilters.cpp => content/svg/content/src/SVGFEDistantLightElement.h
Bug 832155: Convert SVGFEDistantLightElement to WebIDL r=Ms2ger