Moved 2 tests to visuren/ folder along with reference files.

--HG--
rename : css21/reference/anonymous-boxes-001a-ref.xht => css21/visuren/anonymous-boxes-001a-ref.xht
rename : css21/anonymous-boxes-001a.xht => css21/visuren/anonymous-boxes-001a.xht
rename : css21/reference/anonymous-boxes-001b-ref.xht => css21/visuren/anonymous-boxes-001b-ref.xht
rename : css21/anonymous-boxes-001b.xht => css21/visuren/anonymous-boxes-001b.xht
rename : css21/support/1x1-green.png => css21/visuren/support/1x1-green.png