Creates a curve polygon from a multi curve containing an exterior ring and an optional list of interior rings.
SELECT NEW ST_CurvePolygon( NEW ST_MultiCurve( 'MultiCurve(CircularString( -2 0, 4 0, -2 0 ),(0 0, 2 0, 1 1, 0 0 ))' ) )
SQL/MM (ISO/IEC 13249-3: 2006) Vendor extension