2009-10-20 haftmann 2009-10-20 replaced old_style infixes eq_set, subset, union, inter and variants by generic versions
2009-10-15 wenzelm 2009-10-15 replaced String.concat by implode; replaced String.concatWith by space_implode; replaced (Seq.flat o by Seq.maps; replaced List.mapPartial by map_filter; replaced List.concat by flat; replaced (flat o map) by maps, which produces less garbage;
2009-07-17 wenzelm 2009-07-17 tuned/modernized Envir.subst_XXX;
2009-06-23 haftmann 2009-06-23 tuned interfaces of datatype module
2009-06-23 haftmann 2009-06-23 uniformly capitialized names for subdirectories