added abstract to paths in Parse* to make them find Constructions and Documentation

src/abstract/Lang.gf

@@ -8,8 +8,8 @@
 abstract Lang = 
   Grammar, 
   Lexicon
-  ,Construction  --- can be compiled here, but not in concretes, as they call Syntax and Grammar
-  ,Documentation
+--  ,Construction  --- could be compiled here, but not in concretes, as they call Syntax and Grammar
+--  ,Documentation
   ** {
   flags startcat=Phr ;
   } ;