Also on the short-lived `buildbot-custom` branch.

* bpo-30538: Update count() in Functional HOWTO

* bpo-30538: Update enumerate() arguments in Functional HOWTO

Metaprogramming a list of attributes was excessive, and made the code less readable and slower.

Initially the macOS builds are allowed to fail until such time that they can be determined to be stable and not add an unacceptable amount of time to the overall Travis-passing process.

* Fix bpo-30526: Add TextIOWrapper.reconfigure()

* Apply Nick's improved wording

* Update Misc/NEWS

We get `ERROR_BAD_NETPATH` (53) on AppVeyor which is translated to
ENOENT (2).

* bpo-30544: _io._WindowsConsoleIO.write raises the wrong error when WriteConsoleW fails

* bpo-30544: _io._WindowsConsoleIO.write raises the wrong error when WriteConsoleW fails

* bpo-30052: Always regenerate cross-references

The patch for bpo-30052 changed the preferred link target
for :func:`bytes` and :func`bytearray` references to be the
respective type definitions rather than the corresponding
builtin function entries.

This patch changes the daily documentation builds to disable
the output caching in Sphinx, in order to ensure that
cross-reference changes like this one are reliably picked
up and applied automatically after merging.

Also speed up slot_sq_item.

* add test to check if were modifying token

* copy list so import tokenize doesnt have side effects on token

* shorten line

* add tokenize tokens to token.h to get them to show up in token

* move ERRORTOKEN back to its previous location, and fix nitpick

* copy comments from token.h automatically

* fix whitespace and make more pythonic

* change to fix comments from @haypo

* update token.rst and Misc/NEWS

* change wording

* some more wording changes

Bugfix: This test wasn't being run because it was skipping based on the
presence of Py_ENABLE_SHARED rather than its value.  It is always present
on POSIX systems but defaults to 0.

Refactoring: Move the environment variables that can be ignored into a
function.  Parse the list from the child process and filter out the ones
to exclude in the parent before checking that the rest is empty.

Feature: Adds always present environment variables to ignore when
running in a Gentoo sandbox so that the test can pass there.

Replace `an ModuleNotFoundError` with `a ModuleNotFoundError`.
Replace `an path` with `a path`.

Instead use keyword only arguments to os.register_at_fork for each of the scenarios.
Updates the documentation for clarity.

Rather than saving the Python object and calling PyObject_IsTrue()
every time when the boolean argument is used, call it only once and
save C boolean value.

* bpo-16500: Use register_at_fork() in the threading module

* Update comment at top of _after_fork()

Patch by Cheryl Sabella.

* Doc nits for bpo-16500

* Fix more references

Coverage is now 100%

* bpo-30492: Allow make clinic to work out of tree.

* Use os.curdir instead of "." as the default value.

Patch by Cheryl Sabella.

Extension modules listed after the *disabled* marker are not built at all,
neither by the Makefile nor by setup.py.

* bpo-16500: Allow registering at-fork handlers

* Address Serhiy's comments

* Add doc for new C API

* Add doc for new Python-facing function

* Add NEWS entry + doc nit

Calling Ctypes functions is deprecated in 3.6.2 and will be removed in 3.7