bpo-29347: Fix possibly dereferencing undefined pointers when creating weakref objects (#128) (#187)

(cherry picked from commit b2ee40ed)

It was accidentally added in cc798377.

Change the documentation's `Show Source` link on the left menu
to GitHub source file.

* Support "bpo-" in Misc/NEWS (#1)
Change the url to 2.7

(cherry picked from commit 79ab8be0)

* pyspecific.py: remove space after` bpo-`

There were some grammatical errors in weakref.WeakValueDictionary
documentation.

Add canonical header link on each page to corresponding major version of the documentation.

Patch by Matthias Bussonnier.

using PySlice_GetIndicesEx() in debug builds.

variables.

buffer object with custom index object.

Some of the details of comparing mixed types were incorrect or ambiguous.
Added default behaviour and consistency suggestions for user-defined classes.
Based on patch from Andy Maier.

Patch contributed by Mariatta Wijaya.

exited to a stopped instead of terminated state (ex: when under ptrace).

Patch by Serhiy Storchaka.

* Mark up ``--help`` to avoid generating an en dash
* Use forward slash in Unix command line with a dollar sign ($) prompt

ctypes.CDLL instances.

Thanks Greg Bengeult for the patch.

Original patch by Chi Hsuan Yen.