regression: nested aggregation support

tests/modules.a

@@ -1,5 +1,8 @@
 LOAD MODULE FROM "test.so" 
 FUNCTIONS (
-    div(a:int, b:int) -> double, 
+    mydiv(a:int, b:int) -> double, 
     mulvec(a:int, b:vecfloat) -> vecfloat
-);
+);
+
+select mydiv(2,3);
+

tests/stock.a

@@ -18,15 +18,15 @@ INSERT INTO stocks VALUES(15,2)
 INSERT INTO stocks VALUES(16,5)
 
 /*<k> "q1" </k>*/
--- SELECT max(price-min(timestamp)) FROM stocks
+SELECT max(price-min(timestamp)) FROM stocks
 
 /*<k> "q2" </k>*/
--- SELECT max(price-mins(price)) FROM stocks
+SELECT max(price-mins(price)) FROM stocks
 
 /*<k> "q3"</k>*/
 SELECT price, timestamp FROM stocks where price - timestamp > 1 and not (price*timestamp<100)
 
 /*<k> "q4"</k>*/
--- SELECT max(price-mins(price))
--- FROM stocks
---     ASSUMING DESC timestamp
+SELECT max(price-mins(price))
+FROM stocks
+   ASSUMING DESC timestamp