a major refactoring in the C and the Haskell runtimes. Note incompatible change in the PGF format!!!

The following are the outcomes:

   - Predef.nonExist is fully supported by both the Haskell and the C runtimes

   - Predef.BIND is now an internal compiler defined token. For now
     it behaves just as usual for the Haskell runtime, i.e. it generates &+.
     However, the special treatment will let us to handle it properly in 
     the C runtime.

   - This required a major change in the PGF format since both 
     nonExist and BIND may appear inside 'pre' and this was not supported
     before.

src/runtime/haskell/PGF/Morphology.hs

@@ -36,8 +36,8 @@ collectWords pinfo = Map.fromListWith (++)
                          , sym <- elems (sequences pinfo ! seqid)
                          , t <- sym2tokns sym]
   where
-    sym2tokns (SymKS ts)      = ts
-    sym2tokns (SymKP ts alts) = ts ++ [t | Alt ts ps <- alts, t <- ts]
+    sym2tokns (SymKS t)       = [t]
+    sym2tokns (SymKP ts alts) = concat (map sym2tokns ts ++ [sym2tokns sym | (syms,ps) <- alts, sym <- syms])
     sym2tokns _               = []
 
 lookupMorpho :: Morpho -> String -> [(Lemma,Analysis)]