[1.5.x] Modified tutorial 3 to use RequestContext in place of Context.

Backport of df4a74d709 from master
[1.5.x] Fixed error in last commit. Thanks Simon Charette.

Backport of 6ef199a08e from master
[1.5.x] Fixed #19319 -- Updated example httpd.conf for Apache 2.4

Thanks colinnkeenan@ for the report.

Backport of 7314007c5b from master
[1.5.x] Fixed #20612 -- Fixed incorrect wording in CBV documentation

Thanks to ndokos for the report.

Backport of b53ed5ac55d5881f129c4921199af355e2b13565 from master.
[1.5.x] Fixed #19881 -- Documented that get_next/previous_by_FOO uses default manager.

Backport of ba610cb319 from master
Fixed #20634 - Corrected doc mistake re: staticfiles finders strategy.

Thanks claudep for the catch and bmispelon for the research.

Backport of 9be93aa809 from master.
[1.5.x] Fixed errors and inconsistencies in CBV topic documentation.

Backport of bd9fbd1497edc585c5bec28c7d4bc8d1afd1943b from master.
[1.5.x] Corrected minor typos in FileUploadHandler.receive_data_chunk docs.

Backport of 6466a08 from master.
[1.5.x] Clarified get_list_or_404 docs, refs #14150.

Backport of e161e4ff11 from master
[1.5.x] Fixed #20636 -- Stopped stuffing values in the settings.

In Django < 1.6, override_settings restores the settings module that was
active when the override_settings call was executed, not when it was
run. This can make a difference when override_settings is applied to a
class, since it's executed when the module is imported, not when the
test case is run.

In addition, if the settings module for tests is stored alongside the
tests themselves, importing the settings module can trigger an import
of the tests. Since the settings module isn't fully imported yet,
class-level override_settings statements may store a reference to an
incorrect settings module. Eventually this will result in a crash during
test teardown because the settings module restored by override_settings
won't the one that was active during test setup.

While Django should prevent this situation in the future by failing
loudly in such dubious import sequences, that change won't be backported
to 1.5 and 1.4. However, these versions received the "allowed hosts"
patch and they're prone to "AttributeError: 'Settings' object has no
attribute '_original_allowed_hosts'". To mitigate this regression, this
commits stuffs _original_allowed_hosts on a random module instead of the
settings module.

This problem shouldn't occur in Django 1.6, see #20290, but this patch
will be forward-ported for extra safety.

Also tweaked backup variable names for consistency.
[1.5.x] Fixed #20654 -- Fixed type of `m2m_changed`'s `pk_set` arg in docs

Backport of 9a2b07f1b4 from master