[1.6.x] Fixed #20292: Pass datetime objects (not formatted dates) as params to Oracle

This seems worthwhile in its own right, but also works around an Oracle
bug (in versions 10 -- 11.1) where the use of Unicode would reset the
date/time formats, causing ORA-01843 errors.

Thanks Trac users CarstenF for the report, jtiai for the initial patch,
and everyone who contributed to the discussion on the ticket.

Backport of 6983201 from master.

tests/model_fields/tests.py

@@ -20,7 +20,7 @@ from django.utils import unittest
 
 from .models import (Foo, Bar, Whiz, BigD, BigS, Image, BigInt, Post,
     NullBooleanModel, BooleanModel, DataModel, Document, RenamedField,
-    VerboseNameField, FksToBooleans)
+    DateTimeModel, VerboseNameField, FksToBooleans)
 
 
 class BasicFieldTests(test.TestCase):
@@ -154,6 +154,17 @@ class DateTimeFieldTests(unittest.TestCase):
         self.assertEqual(f.to_python('01:02:03.999999'),
                          datetime.time(1, 2, 3, 999999))
 
+    def test_datetimes_save_completely(self):
+        dat = datetime.date(2014, 3, 12)
+        datetim = datetime.datetime(2014, 3, 12, 21, 22, 23, 240000)
+        tim = datetime.time(21, 22, 23, 240000)
+        DateTimeModel.objects.create(d=dat, dt=datetim, t=tim)
+        obj = DateTimeModel.objects.first()
+        self.assertTrue(obj)
+        self.assertEqual(obj.d, dat)
+        self.assertEqual(obj.dt, datetim)
+        self.assertEqual(obj.t, tim)
+
 class BooleanFieldTests(unittest.TestCase):
     def _test_get_db_prep_lookup(self, f):
         from django.db import connection