Remove some dead code

* The following modules are no longer used and have been removed completely:

	GF.Compile.Compute.ConcreteLazy
	GF.Compile.Compute.ConcreteStrict
	GF.Compile.Refresh

* The STM monad has been commented out. It was only used in
  GF.Compile.SubExpOpt, where could be replaced with a plain State monad,
  since no error handling was needed. One of the functions was hardwired to
  the Err monad, but did in fact not use error handling, so it was turned
  into a pure function.

* The function errVal has been renamed to fromErr (since it is analogous to
  fromMaybe).

* Replaced 'fail' with 'raise' and 'return ()' with 'done' in a few places.

* Some additional old code that was already commented out has been removed.

src/compiler/GF/CompileOne.hs

@@ -21,7 +21,7 @@ import GF.Grammar.Binary(decodeModule,encodeModule)
 import GF.Infra.Option
 import GF.Infra.UseIO(FullPath,IOE,isGFO,gf2gfo,MonadIO(..),Output(..),putPointE)
 import GF.Infra.CheckM(runCheck')
-import GF.Data.Operations(ErrorMonad,liftErr,(+++))
+import GF.Data.Operations(ErrorMonad,liftErr,(+++),done)
 
 import GF.System.Directory(doesFileExist,getCurrentDirectory,renameFile)
 import qualified Data.Map as Map
@@ -62,7 +62,7 @@ reuseGFO opts srcgr file =
 
      if flag optTagsOnly opts
        then writeTags opts srcgr (gf2gftags opts file) sm1
-       else return ()
+       else done
 
      return (Just file,sm)
 
@@ -132,7 +132,7 @@ compileSourceModule opts cwd mb_gfFile gr =
            idump opts pass (dump out)
            return (ret out)
 
-    maybeM f = maybe (return ()) f
+    maybeM f = maybe done f
 
 
 --writeGFO :: Options -> FilePath -> SourceModule -> IOE ()
@@ -151,12 +151,12 @@ writeGFO opts file mo =
 --intermOut :: Options -> Dump -> Doc -> IOE ()
 intermOut opts d doc
   | dump opts d = ePutStrLn (render ("\n\n--#" <+> show d $$ doc))
-  | otherwise   = return ()
+  | otherwise   = done
 
 idump opts pass = intermOut opts (Dump pass) . ppModule Internal
 
 warnOut opts warnings
-  | null warnings = return ()
+  | null warnings = done
   | otherwise     = do ePutStr "\ESC[34m";ePutStr ws;ePutStrLn "\ESC[m"
   where
     ws = if flag optVerbosity opts == Normal