GF.Infra.Modules: restore module dependency order invariant

It is needed by greatestResource (and similar functions, presumably).
So keep both the list and the finite map of modules. This slows down some
things, but the compilation of PhrasebookFin.pgf benefits from it.
To be continued...

src/compiler/GF/Infra/Modules.hs

@@ -23,13 +23,13 @@ module GF.Infra.Modules (
         mGrammar,modules,
         extends, isInherited,inheritAll, 
         updateMGrammar, updateModule, replaceJudgements, addFlag,
-        addOpenQualif, flagsModule, allFlags, mapModules,
+        addOpenQualif, flagsModule, allFlags,
         OpenSpec(..),
         ModuleStatus(..),
         openedModule, depPathModule, allDepsModule, partOfGrammar,
         allExtends, allExtendSpecs, allExtendsPlus, allExtensions, 
         searchPathModule,
-     -- addModule,
+     -- addModule, mapModules,
         emptyMGrammar, emptyModInfo,
         abstractOfConcrete, abstractModOfConcrete,
         lookupModule, lookupModuleType, lookupInfo,
@@ -51,16 +51,15 @@ import Text.PrettyPrint
 
 -- The same structure will be used in both source code and canonical.
 -- The parameters tell what kind of data is involved.
--- No longer maintained invariant (TH 2011-08-30):
---      modules are stored in dependency order
+-- Invariant: modules are stored in dependency order
 
 --mGrammar = MGrammar
 --newtype MGrammar a = MGrammar {modules :: [(Ident,ModInfo a)]}
 
-newtype MGrammar a = MGrammar {moduleMap :: Map.Map Ident (ModInfo a)}
+data MGrammar a = MGrammar {moduleMap :: Map.Map Ident (ModInfo a),
+                            modules :: [(Ident,ModInfo a)] }
   deriving Show
-modules = Map.toList . moduleMap
-mGrammar = MGrammar . Map.fromList
+mGrammar ms = MGrammar (Map.fromList ms) ms
 
 data ModInfo a = ModInfo {
     mtype   :: ModuleType,
@@ -126,11 +125,10 @@ flagsModule (_,mi) = flags mi
 
 allFlags :: MGrammar a -> Options
 allFlags gr = concatOptions [flags m | (_,m) <- modules gr]
-
+{-
 mapModules :: (ModInfo a -> ModInfo a) -> MGrammar a -> MGrammar a 
---mapModules f (MGrammar ms) = MGrammar (map (onSnd f) ms)
-mapModules f (MGrammar ms) = MGrammar (fmap f ms)
-
+mapModules f = mGrammar . map (onSnd f) . modules
+-}
 data OpenSpec = 
    OSimple Ident
  | OQualif Ident Ident