Clean up INITIAL a bit and add a test case.

There's no need for INITIALs to be early-constant-folded, since -- unlike VALs
-- they can't be used in later constant folding.

frontends/ParseOccam.hs

@@ -1318,8 +1318,8 @@ initialIsAbbrev
            e <- expressionOfType t
            sColon
            eol
-           (e', _, _) <- constantFold e
-           return $ A.Specification m n $ A.IsExpr m A.Original t e'
+           return $ A.Specification m n $ A.IsExpr m A.Original t e
+    <?> "INITIAL IS abbreviation"
 
 isAbbrev :: OccParser A.Name -> OccParser A.Variable -> OccParser A.Specification
 isAbbrev newName oldVar

testcases/initial.occ

@@ -0,0 +1,8 @@
+PROC P ()
+  INITIAL INT x IS 1234:
+  INITIAL []BYTE cs IS "hello, world":
+  SEQ
+    SEQ i = 0 FOR SIZE cs
+      cs[i] := 'A'
+    x := x + 1
+: