output COLLECTION of Polygon for TIN and PolyhedralSurface, for ST_ForceSFS (instead of MultiPolygon). Thanks to Sandro for these input

git-svn-id: http://svn.osgeo.org/postgis/trunk@11402 b70326c6-7e19-0410-871a-916f4a2858ee
Change ST_force_sfs to ST_ForceSFS

git-svn-id: http://svn.osgeo.org/postgis/trunk@11403 b70326c6-7e19-0410-871a-916f4a2858ee