It is not possible to unload a module written in C, so use a subprocess to run
the tests on the module compiled by test_build_ext(). Using a subprocess, we
don't have to unload the module, save/restore sys.path, and the test can be run
more than once.

This commit fixes also an access error on rmtree() on Windows: because the
module was not really unloaded, it was not possible to remove the temporary
directory (it is not possible to remove a directory on Windows if it still
contains an open file).

packaging.tests.support.TempdirManager: rmtree() fails on Windows if there are
still open files in the directory.

multiprocessing: Process._bootstrap() keeps a reference to the old process to
delay its finalization until after _run_after_forkers() as been executed. This
change should fix a crash on Mac OS X Tiger when a lock is released after a
fork.

Patch written by Charles-François Nataliv and Antoine Pitrou.

multiprocessing: Process._bootstrap() keeps a reference to the old process to
delay its finalization until after _run_after_forkers() as been executed. This
change should fix a crash on Mac OS X Tiger when a lock is released after a
fork.

Patch written by Charles-François Nataliv and Antoine Pitrou.

packaging.tests.support.TempdirManager: removing the current directory is not
allowed on Windows or Solaris. Store the current directory and restore it
before removing the temporary directory (which is used as the working directory
during the tests).

Don't modify mutable default arguments...

After 1a3e8db28d49, Windows XP could not os.stat at all due to raising
immediately when GetFinalPathNameByHandle wasn't available (pre-Vista).
The proper behavior in that situation is to just not attempt a traversal
rather than outright rejecting.

This change additionally handles a failed malloc by setting the error code
and returning false.

Patch by Hirokazu Yamamoto.

Use of DeviceIoControl to obtain the symlink path via the reparse tag was
removed. The code now uses GetFinalPathNameByHandle in the case of a
symbolic link and works properly given the added test which creates a symbolic
link and calls os.stat on it from multiple locations.

Victor Stinner also noticed an issue with os.lstat following the os.stat
code path when being passed bytes. The posix_lstat function was adjusted to
properly hook up win32_lstat instead of the previous STAT macro (win32_stat).

Spawn a new process instead of using fork(). Patch written by Charles-François
Natali.

This allows findsource() to work in doctests.

A patch from Dirkjan Ochtman.

methods.