Close #15486: Simplify the mechanism used to remove importlib frames from tracebacks when they just introduce irrelevant noise

faulthandler requires the importlib if "-X faulthandler" option is present on
the command line, so initialize faulthandler after importlib.

Add also an unit test.

'level' values and set its document default value to 0.

Thanks to Arfrever Frehtes Taifersar Arahesis for filing the bug.

Followup to issue #15489.

instead of 100, to be able to display long file paths

the Apple-supplied Tck/Tk versions shipped with OS X 10.7 and 10.8.
They are not as buggy as the 10.6 version but can still easily crash.

Also add tests in the OS X installer build to ensure that the desired
dynamic linking with an optional newer Tcl/Tk in /Library actually
happens.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

Patch by Serhiy Storchaka.

to prevent constant regeneration of importlib.h.

Patch by Amaury Forgeot d'Arc.

Patch by Kristján Valur Jónsson.

to make importlib.h (and other byte code files) equal between 32-bit
and 64-bit systems.

to help pickling of naive subclasses.

form is used in many places in the source tree, but was found to be incorrect
in a recent tracker discussion.

Original patch by J Derek Wilson.