The issue was caused by CDDM_tessfaces_to_faces not dealing with CD layers.
There was already function BKE_mesh_convert_mfaces_to_mpolys which converted
mfaces to mpolys with converting all CD layers. Made it a bit more general so
it might work with given arrays of faces/polys and re-used it from CDDM module.
Checked with UV and sculpt data from Blender 2.61 and it loaded nice, so
hopefully there's no regressions in loading older files.
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