Added a test for negated Q object querying

The added test is from the patch in ticket #19672 (written by Ian
Kelly). Fixed #19672, refs #19849.

tests/regressiontests/queries/models.py

@@ -64,6 +64,7 @@ class Annotation(models.Model):
 class ExtraInfo(models.Model):
     info = models.CharField(max_length=100)
     note = models.ForeignKey(Note)
+    value = models.IntegerField(null=True)
 
     class Meta:
         ordering = ['info']