Use EIdentifier instead of ESymbol Alpha for \ell, etc.

Closes #256.

Author: jgm

src/Text/TeXMath/Readers/TeX.hs

@@ -878,6 +878,7 @@ tSymbol sym =
          (\t -> EUnder False t acc) <$> texToken
        Just acc@(ESymbol TOver _) ->
          (\t -> EOver False t acc) <$> texToken
+       Just (ESymbol Alpha t) -> return $ EIdentifier t -- see #256
        Just x  -> return x
        Nothing
          | sym == "\\mod" -> do

test/regression/235.test

@@ -89,7 +89,7 @@
 , EIdentifier "\953"
 , EIdentifier "\922"
 , EIdentifier "\954"
-, ESymbol Alpha "\120600"
+, EIdentifier "\120600"
 , EIdentifier "\923"
 , EIdentifier "\120556"
 , EIdentifier "\955"
@@ -105,7 +105,7 @@
 , EIdentifier "\928"
 , EIdentifier "\120561"
 , EIdentifier "\960"
-, ESymbol Alpha "\982"
+, EIdentifier "\982"
 , EIdentifier "\929"
 , EIdentifier "\961"
 , EIdentifier "\931"