Fix suggested by Itay Brandes

Patch by Victor Stinner.

Reverts some changes of a36666c52115.

In the case of os's `mknod(filename[, mode=0600[, device=0]])`, I have nested
the [] as setting mode doesn't require to set device (but setting device
requires to set mode).

Mostly just mechanical removal of []. In some rare cases I've pulled the
default value up into the argument list.

It doesn't get called on 'null', 'true', 'false' since f686aced02a3.

Original patch by Stefano Taschini.

sqlite3, such as was shipped with Centos 5 and Mac OS X 10.4.

 Issue #14426: Correct the Date format in Expires attribute of Set-Cookie. Patch by Federico Reghenzani and Müte Invert

Closes #14842.

This appears to have been a mixup introduced when we switched from
'expected/actual' to 'first/second'.  The problem doesn't exist
in the corresponding assertCountEqual method in Python3.

The behaviour of the parse_constant callback changed insofar that 'null',
'true', 'false' don't trigger its call anymore.

Patch by Serhiy Storchaka

undecoded UTF-8 bytes as a string when accessing the Tk clipboard.
Modify clipboad_get() to first request type UTF8_STRING when no
specific type is requested in an X11 windowing environment, falling
back to the current default type STRING if that fails.
Original patch by Thomas Kluyver.