Improve performance of sre_parse._uniq function.

Expose the CAN_BCM SocketCAN constants used in the bcm_msg_head struct
flags (provided by <linux/can/bcm.h>) under the socket library.

This adds the following constants with a CAN_BCM prefix:

  * SETTIMER
  * STARTTIMER
  * TX_COUNTEVT
  * TX_ANNOUNCE
  * TX_CP_CAN_ID
  * RX_FILTER_ID
  * RX_CHECK_DLC
  * RX_NO_AUTOTIMER
  * RX_ANNOUNCE_RESUME
  * TX_RESET_MULTI_IDX
  * RX_RTR_FRAME
  * CAN_FD_FRAME

The CAN_FD_FRAME flag was introduced in the 4.8 kernel, while the other
ones were present since SocketCAN drivers were mainlined in 2.6.25. As
such, it is probably unnecessary to guard against these constants being
missing.

* bpo-33821: Update IDLE section of What's New 3.7

* Fix roles.

* bpo-33822: Add IDLE section of What's New 3.8

* Fix role.

* Fix typos in comments, docs and test names

* Update test_pyparse.py

account for change in string length

* Apply suggestion: splitable -> splittable
Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: splitable -> splittable
Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Apply suggestion: Dealloccte -> Deallocate
Co-Authored-By: Terry Jan Reedy <tjreedy@udel.edu>

* Update posixmodule checksum.

* Reverse idlelib changes.

This looks like the only place that proto 4 framing gets exercised
so leave it as part of the PGO task.

Mark some individual tests to skip when --pgo is used.  The tests
marked increase the PGO task time significantly and likely don't
help improve optimization of the final executable.

Use cffi to access a C API in Python.

When scanning the string, most characters are valid, so
checking for invalid characters first means never needing
to check the value of strict on valid strings, and only
needing to check it on invalid characters when doing
non-strict parsing of invalid strings.

This provides a measurable reduction in per-character
processing time (~11% in the pre-merge patch testing).

Deprecate the parser module and add a deprecation warning triggered on import and a warning block in the documentation.





https://bugs.python.org/issue37268



Automerge-Triggered-By: @pablogsal

They pass with tk 8.5.9 (Azure) but fail with the 8.6.x we install.

https://bugs.python.org/issue36044



Automerge-Triggered-By: @zooba

* bpo-37697: Sync with importlib_metadata 0.19

* Run make regen-importlib

* 📜🤖 Added by blurb_it.

Use an example shell interaction in the sample and better labels for shell elements.

The boxes for the font and highlight samples are now constrained by the overall config dialog size.  They gain scrollbars when the when a large font size makes the samples too large for the box.

Add __all__ to tkinter.__init__ and submodules.  Replace 'import *'
with explicit imports in some submodules.

Previously, pyc files in the embeddable distribution reported their
location as <build path>/<file stem>.py. This causes a little confusion
when interpreting stack traces as the file is in a (almost certainly)
incorrect location, and lacks the full relative path to Lib (e.g.
email/mime/image.py will only show image.py).

This change preserves the Lib relative location of the source file as a
path so that stack traces are (hopefully) less misleading and more
informative.
Co-Authored-By: Kyle Stanley <aeros167@gmail.com>

Prior to this change the guard on an 'elif' used an assignment expression whose value was used in a later 'else' block, causing some confusion for people.

(Discussion on Twitter: https://twitter.com/brettsky/status/1153861041068994566.)

Automerge-Triggered-By: @brettcannon