Represent identifiers as UTF-8-encoded ByteStrings

This was a fairly simple change thanks to previous work on making the Ident
type abstract and the fact that PGF.CId already uses UTF-8-encoded
ByteStrings.

One potential pitfall is that Data.ByteString.UTF8 uses the same type for
ByteStrings as Data.ByteString. I renamed ident2bs to ident2utf8 and
bsCId to utf8CId, to make it clearer that they work with UTF-8-encoded
ByteStrings.

Since both the compiler input and identifiers are now UTF-8-encoded
ByteStrings, the lexer now creates identifiers without copying any characters.
**END OF DESCRIPTION***

Place the long patch description above the ***END OF DESCRIPTION*** marker.
The first line of this file will be the patch name.


This patch contains the following changes:

M ./src/compiler/GF/Compile/CheckGrammar.hs -3 +3
M ./src/compiler/GF/Compile/GrammarToPGF.hs -2 +2
M ./src/compiler/GF/Grammar/Binary.hs -5 +1
M ./src/compiler/GF/Grammar/Lexer.x -11 +13
M ./src/compiler/GF/Infra/Ident.hs -19 +36
M ./src/runtime/haskell/PGF.hs -1 +1
M ./src/runtime/haskell/PGF/CId.hs -2 +3

src/compiler/GF/Grammar/Binary.hs

@@ -30,7 +30,7 @@ import PGF.Data(Literal(..))
 gfoVersion = "GF03"
 
 instance Binary Ident where
-  put id = put (ident2bs id)
+  put id = put (ident2utf8 id)
   get    = do bs <- get
               if bs == BS.pack "_"
                 then return identW
@@ -295,10 +295,6 @@ instance Binary Label where
              1 -> fmap LVar   get
              _ -> decodingError
 
-instance Binary RawIdent where
-  put = put . rawId2bs
-  get = fmap rawIdentC get
-
 --putGFOVersion = mapM_ (putWord8 . fromIntegral . ord) gfoVersion
 --getGFOVersion = replicateM (length gfoVersion) (fmap (chr . fromIntegral) getWord8)
 --putGFOVersion = put gfoVersion