Fix bugs in checks for varying parameters in exported functions.

In short, we inadvertently weren't checking whether pointers themselves
were varying, which in turn led to an assertion later if an exported
function did have a varying parameter.

Issue #187.

module.cpp

@@ -343,8 +343,6 @@ Module::AddGlobalVariable(Symbol *sym, Expr *initExpr, bool isConst) {
 */
 static bool
 lRecursiveCheckValidParamType(const Type *t) {
-    t = t->GetBaseType();
-
     const StructType *st = dynamic_cast<const StructType *>(t);
     if (st != NULL) {
         for (int i = 0; i < st->GetElementCount(); ++i)
@@ -352,15 +350,16 @@ lRecursiveCheckValidParamType(const Type *t) {
                 return true;
         return false;
     }
-    else {
-        if (t->IsVaryingType())
-            return true;
-        const PointerType *pt = dynamic_cast<const PointerType *>(t);
-        if (pt != NULL && pt->IsSlice())
-            return true;
-        else
-            return false;
-    }
+
+    const SequentialType *seqt = dynamic_cast<const SequentialType *>(t);
+    if (seqt != NULL)
+        return lRecursiveCheckValidParamType(seqt->GetElementType());
+
+    const PointerType *pt = dynamic_cast<const PointerType *>(t);
+    if (pt != NULL)
+        return (pt->IsSlice() || pt->IsVaryingType());
+
+    return t->IsVaryingType();
 }