openjpeg20: may break formulae in main repo; for gdal 1.10 support

See also (why PR to `versions` instead of main rep): closed PR https://github.com/mxcl/homebrew/pull/16573

Added to versions to allow keg-only linking to `gdal` 1.10 for its [`JP2OpenJPEG` support](http://www.gdal.org/frmt_jp2openjpeg.html).