Backport enhancements from master, commits:

* 9c4bfa66: "make tags": remove -t
  option of ctags. The option was kept for backward compatibility,
  but it was completly removed recently. Patch written by Stéphane
  Wirtel.
* cf0ac6a7: Fix "make tags": set
  locale to C to call sort
* 8a543c0b: `make tags` fixes (GH-717)

Ignore more generated files.

(cherry picked from commit 6fde770e)

(cherry picked from commit 85157cd8)

(cherry picked from commit 8e675286)

Reported by Sean Canavan on docs@p.o.

(cherry picked from commit 8526fb74)

[2.7] [3.5] bpo-30070: Fixed leaks and crashes in errors handling in the parser module. (GH-1131). (GH-1185) (#1189)

(cherry picked from commit a79f4c21).
(cherry picked from commit 952a05e4e2cf082b74a1676a2804f1f43a9b7702)

[2.7] bpo-30061: Check if PyObject_Size()/PySequence_Size()/PyMapping_Size() (GH-1096) (GH-1180) (#1183)

raised an error.

(cherry picked from commit bf623ae8)
(cherry picked from commit 680fea4)

PySlice_GetIndicesEx in _ctypes.c.

* Remove conditional on free of `dps`, since `dps` is now allocated for
all versions of OpenSSL
* Remove call to `x509_check_ca` since it was only used to cache
the `crldp` field of the certificate
CRL_DIST_POINTS_free is available in all supported versions of OpenSSL
(recent 0.9.8+) and LibreSSL.
(cherry picked from commit 2849cc34)

And fix the parameter name.

(cherry picked from commit 8fc7bc2b)

(cherry picked from commit 3d707be9)

(cherry picked from commit 01fa9ae5)

The reference to administrative data was confusing to readers,
so this simplifies the note to explain that deep copying may copy
more then you intended, such as data that you expected to be
shared between copies.

Patch by Sanyam Khurana.

The original attempted fix missed an `isdir()` call in
`get_base_branch()`.

(cherry picked from commit b879fe82)

* Keep the c-api exception doc up-to-date

cherry-pick'ed from ec1f5df4..e3d6db3 and fix conflict

(cherry picked from commit 060d2d77)

* bpo-28087: Skip test_asyncore and test_eintr poll failures on macOS

Skip some tests of select.poll when running on macOS due to unresolved
issues with the underlying system poll function on some macOS versions.

(cherry picked from commit de046446)

* Fix socket leaks

* Fixed sockets leak

(cherry picked from commit 576def09)

(cherry picked from commit a6b4e1902250d6f28ca6d083ce1c8d7e9b91974b)

s/keys and elements/keys and values/
(cherry picked from commit cdcac039)

Fix the use of recursion in itertools.chain.from_iterable. Using recursion
is unnecessary, and can easily cause stack overflows, especially when
building in low optimization modes or with Py_DEBUG enabled.
(cherry picked from commit 5466d4af)

when pass indices of wrong type.
(cherry picked from commit d4edfc9a)
(cherry picked from commit bf4bb2e43030661e568d5d4b046e8b9351cc164c)

(cherry picked from commit c3c7ef08)

(cherry picked from commit 0ae7c8bd)

The presence of the ``--enable-optimizations`` flag is indicated by the
value of ``$enableval``, but the configure script was checking ``$withval``,
resulting in the ``--enable-optimizations`` flag being effectively ignored.
(cherry picked from commit 8cea5929)

Instead have gcc be used for the coverage build so gcc is exercised in at least one place.
(cherry picked from commit ad2f9e2c)