Guess that Nom+Acc become Gen in negative, remove neggen field

This removes around 70k concrete categories (in PGFs compiled with
--optimize-pgf.)
Unsure if that is actually useful -- the number of concrete functions
only went down by a couple hundred.

src/russian/ParamRus.gf

@@ -105,7 +105,7 @@ oper
     -- refl : Reflexivity ;
     -- tran : Transitivity
     } ;
-  ComplementCase : Type = {s : Str ; c : Case ; neggen : Bool ; hasPrep : Bool} ;
+  ComplementCase : Type = {s : Str ; c : Case ; hasPrep : Bool} ;
   VerbForms2 : Type = VerbForms ** {c : ComplementCase} ;
   VerbForms3 : Type = VerbForms ** {c : ComplementCase ; c2 : ComplementCase} ;
 
@@ -115,4 +115,11 @@ oper
       <_,Transitive> => Trans ;
       <_,Intransitive> => Intrans
     } ;
+
+  -- Whether the noun that the preposition governs turns genitive in negative context
+  -- NB. I'm just guessing here, this is an exercise in shaving concrete categories. /IL
+  neggen : ComplementCase -> Bool = \c -> case c.c of {
+    Nom|Acc => True ;
+    _       => False
+    } ;
 }

src/russian/ResRus.gf

@@ -1563,7 +1563,7 @@ oper
   applyPolPrep : Polarity -> ComplementCase -> NounPhrase -> Str
     = \pol,prep,np ->
       let prep'=prep ** {
-        c=case <pol, prep.neggen> of {<Neg, True> => Gen ; _ => prep.c}
+        c=case <pol, neggen prep> of {<Neg, True> => Gen ; _ => prep.c}
       } in applyPrep prep' np ;
 
   applyIPronPrep : ComplementCase -> IPronounForms -> Str

src/russian/VerbRus.gf

@@ -114,7 +114,7 @@ lin
         PrefShort => ap.short
         } ;
       Neg => case ap.preferShort of {
-        PreferFull => case v2a.c.neggen of {
+        PreferFull => case neggen v2a.c of {
             False => \\a => ap.s ! agrGenNum a ! Animate ! v2a.c.c ;
             True => \\a => ap.s ! agrGenNum a ! Animate ! Gen
           } ;