commented out Documentation definitions in notpresent mode. It was not enough to do this in the import list in Lang, since the import list parsing seems to be done without preprocessing.

src/abstract/Lang.gf

@@ -9,7 +9,7 @@ abstract Lang =
   Grammar, 
   Lexicon
   ,Construction  --- could be compiled here, but not in concretes, as they call Syntax and Grammar
-  ,Documentation
+  ,Documentation  --# notpresent
   ,Markup - [stringMark]
   ** {
   flags startcat=Phr ;