Stopped the expansion of inner array literals into subscripted elements

This expansion was causing a big blow-up in the code, as things like:

VAL [2][1]INT as IS [[0,1]]

were getting transformed into:

VAL [2]INT n0 IS [0,1]:
VAL [2]INT n1 IS [0,1]:
VAL [2]INT n2 IS [n0[0], n1[1]]:
VAL [2][1]INT as IS [n2]:

Or something similar -- the inner arrays were pulled up into multiple definitions that were then subscripted, because the first pull-up did this:

VAL [2]INT n2 IS [[0,1][0], [0,1][1]]:

and then the inner arrays got pulled up again, separately.  The change hasn't immediately broken anything, but I haven't fully tested it yet

transformations/SimplifyExprs.hs

@@ -128,8 +128,9 @@ expandArrayLiterals = pass "Expand array literals"
     doArrayElem :: A.Structured A.Expression -> PassM (A.Structured A.Expression)
     doArrayElem ae@(A.Only _ e)
         =  do t <- astTypeOf e
-              case t of
-                A.Array ds _ -> expand ds e
+              case (t, e) of
+                (A.Array {}, A.Literal {}) -> return ae
+                (A.Array ds _, _) -> expand ds e
                 _ -> return ae
     doArrayElem ae = return ae