add cases with lowercase null

Author: safareli

test/src/Parse.purs

@@ -63,6 +63,10 @@ testSuite1 = do
     SELECT * FROM `/smallZips.json` WHERE city IS NOT "foo"
   """
 
+  parseSucc """
+    SELECT * FROM `/smallZips.json` WHERE city IS null
+  """
+
   parseSucc """
     SELECT * FROM `/smallZips.json` WHERE city IS NULL
   """
@@ -71,6 +75,10 @@ testSuite1 = do
     SELECT * FROM `/smallZips.json` WHERE city IS NOT NULL
   """
 
+  parseSucc """
+    SELECT * FROM `/smallZips.json` WHERE city IS NOT null
+  """
+
   parseSucc """
     select a from `/f` where b is not between 1 and (2..3)
   """