Fixed #1142 -- Added multiple database support.

This monster of a patch is the result of Alex Gaynor's 2009 Google Summer of Code project.
Congratulations to Alex for a job well done.

Big thanks also go to:
 * Justin Bronn for keeping GIS in line with the changes,
 * Karen Tracey and Jani Tiainen for their help testing Oracle support
 * Brett Hoerner, Jon Loyens, and Craig Kimmerer for their feedback.
 * Malcolm Treddinick for his guidance during the GSoC submission process.
 * Simon Willison for driving the original design process
 * Cal Henderson for complaining about ponies he wanted.

... and everyone else too numerous to mention that helped to bring this feature into fruition.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@11952 bcc190cf-cafb-0310-a4f2-bffc1f526a37

tests/regressiontests/multiple_database/models.py

@@ -0,0 +1,49 @@
+from django.conf import settings
+from django.contrib.auth.models import User
+from django.contrib.contenttypes.models import ContentType
+from django.contrib.contenttypes import generic
+from django.db import models, DEFAULT_DB_ALIAS
+
+class Review(models.Model):
+    source = models.CharField(max_length=100)
+    content_type = models.ForeignKey(ContentType)
+    object_id = models.PositiveIntegerField()
+    content_object = generic.GenericForeignKey()
+
+    def __unicode__(self):
+        return self.source
+
+    class Meta:
+        ordering = ('source',)
+
+class PersonManager(models.Manager):
+    def get_by_natural_key(self, name):
+        return self.get(name=name)
+
+class Person(models.Model):
+    objects = PersonManager()
+    name = models.CharField(max_length=100)
+
+    def __unicode__(self):
+        return self.name
+
+    class Meta:
+        ordering = ('name',)
+
+class Book(models.Model):
+    title = models.CharField(max_length=100)
+    published = models.DateField()
+    authors = models.ManyToManyField(Person)
+    editor = models.ForeignKey(Person, null=True, related_name='edited')
+    reviews = generic.GenericRelation(Review)
+
+    def __unicode__(self):
+        return self.title
+
+    class Meta:
+        ordering = ('title',)
+
+class UserProfile(models.Model):
+    user = models.OneToOneField(User)
+    flavor = models.CharField(max_length=100)
+