+ 12.1.2001 Goetz
+ Added implementation of overwrites stuff.
+
+ 11.7.2001 Goetz
+ Implemented stuff to change the type graph. See
+ typegmod.h and tpop.h for basic documentation of the change.
+ There now exists a type of kind type_id. If this appears
+ externally this is a bug.
+
+ 9.7.2001 Goetz
+ Added some new access routines to types.
+ List of overwritten fields for entities.
+ Removed a bug in irnode.
+
+ 4.7.2001 Goetz
+ Added a routine to set the mangled entity name.
+ Added two routines to copy entites.
+
3.7.2001 Goetz
Entities now have two more flags, for visibility and allocation mode.
Types that have a layout have a flag indicating whether the layout is