Issue #18571: Implementation of the PEP 446: file descriptors and file handles
are now created non-inheritable; add functions os.get/set_inheritable(),
os.get/set_handle_inheritable() and socket.socket.get/set_inheritable().
Fix compilation of the _sqlite module if threads are disabled
(Merge 3.3) Fix compilation of the _sqlite module if threads are disabled
pythonrun.c: use MAXPATHLEN instead of PATH_MAX

PATH_MAX is not available on "MIPS IRIX 6.5.30 [SB] 3.x" buildbot
fix a compilation warning in posix_openpty() on "PPC64 AIX 3.x" buildbot
_datetimemodule.c: fix the compilation warning "conversion from 'double' to
'long', possible loss of data" in delta_new(), use an explicit cast from double
to long
Get rid of signed/unsigned comparaison in _sre.c

Fix compilation warnings on Windows (Visual C++) like: "_sre.c(3121): warning
C4018: '>' : signed/unsigned mismatch".

_validate_outer() ensures that groups >= 0, so _validate_inner() can cast
groups to size_t.
Issue #18865: PEP 446 makes multiprocessing.util.pipe() unnecessary.
Issue #18865: remove unused import from multiprocessing.util.spawnv_passfds()
select.epoll.fromfd(fd) must be not change the inheritable flag of the file
descriptor
test_posix.test_pipe2() now checks that the O_NONBLOCK flag is set

Use also os.get_inheritable() instead of fcntl() to check the inheritable flag
(FD_CLOEXEC).
Fix @requires_freebsd_version and @requires_linux_version decorators of
test.support, run the test if the platform matchs!
Fix test_socket.test_SOCK_CLOEXEC(), the test was wrong
(Merge 3.3) Fix @requires_freebsd_version and @requires_linux_version
decorators of test.support, run the test if the platform matchs!
Issue #18786: Don't reinstall old SIGUSR1 handler prematurely.
Issue #11798: TestSuite now drops references to own tests after execution.
Fix tests for #11798
Tighten-up the lookkey() logic and beautify the code a bit.

Use less code by moving many of the steps from the initial
lookup into the main search loop.

Beautify the code but keep the overall logic unchanged.
Issue #18760: Improved cross-references in the xml package.
Issue #18760: Improved cross-references in the xml package.