(cherry picked from commit cb04f751)

bpo-31770: Prevent a crash and refleaks when calling sqlite3.Cursor.__init__() more than once (GH-3968) (#4302)

(cherry picked from commit e56ab746)

(cherry picked from commit aafece7a)

(cherry picked from commit b838cc3f)

* Using ifconfig on NetBSD and OpenBSD.
* Using arp on Linux, FreeBSD, NetBSD and OpenBSD.

Based on patch by Takayuki Shimizukawa..
(cherry picked from commit ee1a9a2b)

(cherry picked from commit a7723d8b)

Bug report and patch by Jeroen Demeyer..
(cherry picked from commit f6f90ff0)

(cherry picked from commit 4f469c09)

(cherry picked from commit 894ebd06)

bpo-31910: test_create_connection() now catchs also EADDRNOTAVAIL to
fix the test on Travis CI.
(cherry picked from commit 280c22a8)

Modify the code to use ncurses is_pad() instead of checking WINDOW
_flags field.  If your platform does not provide the is_pad(), the
existing way that checks the field will be enabled.

Note: This change does not drop support for platforms where do not
have both WINDOW _flags field and is_pad().
(cherry picked from commit 8bc7d635)

* Fix a compilation error on FreeBSD.
* Fix the data attribute size on Mac OS X.
(cherry picked from commit 2298fad5)

Document the following functions:

* PyObject_Malloc()
* PyObject_Realloc()
* PyObject_Free()

Document also the pymalloc allocator.

* Fixed the layout of the kqueue_event structure on OpenBSD and NetBSD.
* Fixed the comparison of the kqueue_event objects..
(cherry picked from commit b9052a0f)

(cherry picked from commit baac01e6)

test_curses now saves/restores signals. On FreeBSD, the curses module
sets handlers of some signals, but don't restore old handlers when
the module is deinitialized.

(cherry picked from commit 19f68301)

separators that are not bytes-like objects..
(cherry picked from commit a2314283)

GCC says:
../cpython/Python/marshal.c: In function ‘PyMarshal_WriteLongToFile’:
../cpython/Python/marshal.c:70:35: warning: ‘wf.ptr’ may be used uninitialized in this function [-Wmaybe-uninitialized]
                       else if ((p)->ptr != (p)->end) *(p)->ptr++ = (c); \
                                   ^~
../cpython/Python/marshal.c:70:47: warning: ‘wf.end’ may be used uninitialized in this function [-Wmaybe-uninitialized]
                       else if ((p)->ptr != (p)->end) *(p)->ptr++ = (c); \
                                               ^~
../cpython/Python/marshal.c:77:10: warning: ‘wf.str’ may be used uninitialized in this function [-Wmaybe-uninitialized]
     if (p->str == NULL)
         ~^~~~~

This isn't a real problem because if the file pointer is not NULL, the
string-related fields are never touched. But, it doesn't hurt to set the unused
fields to NULL.

(cherry picked from commit f52dff611cff2fb9e90340b4787eda50ab2d40c6)

* Fix incorrect links.
* Remove redundant links.
* Add signatures and index entries for gettext related
functions in the locale module.
(cherry picked from commit c02a1f4a)

[2.7] bpo-31752: Fix possible crash in timedelta constructor called with custom integers. (GH-3947) (#4088)

Bad remainder in divmod() in intermediate calculations caused an assertion failure..
(cherry picked from commit 4ffd4653)

(cherry picked from commit bcbdd2f8)

The word "difference" from missing the sentence.
This clarifies that it compares the difference between the two objects.
(cherry picked from commit 032a6480)

Always pass -1, or INFTIM where defined, to the poll() system call when
a negative timeout is passed to the poll.poll([timeout]) method in the
select module. Various OSes throw an error with arbitrary negative
values..
(cherry picked from commit 6cfa927c)

[2.7] bpo-31786: Make functions in the select module blocking when timeout is a small negative value. (GH-4003). (#4031)

(cherry picked from commit 2c15b29a)

bpo-31733, bpo-31692: Document the new PYTHONSHOWREFCOUNT and
PYTHONSHOWALLOCCOUNT environment variables.

bpo-31692, bpo-19527:

* Add a new PYTHONSHOWALLOCCOUNT environment variable, similar to
  the Python 3 "-X showalloccount" option
* When Python is compiled with COUNT_ALLOCS, the new
  PYTHONSHOWALLOCCOUNT environment variable now has to be set to dump
  allocation counts into stderr on shutdown. Moreover, allocations
  statistics are now dumped into stderr rather than stdout.
* Add @test.support.requires_type_collecting decorator: skip test if
  COUNT_ALLOCS is defined
* Fix tests for COUNT_ALLOCS: decorate some methods with
  @requires_type_collecting
* test_sys.test_objecttypes(): update object type when COUNT_ALLOCS
  is defined

Add a new PYTHONSHOWREFCOUNT environment variable. In debug mode,
Python now only print the total reference count if PYTHONSHOWREFCOUNT
is set.

(cherry picked from commit de072100)

[2.7] bpo-31490: Fix an assertion failure in ctypes in case an _anonymous_ attr is defined only outside _fields_. (GH-3615) (#3952)

[2.7] bpo-31728: Prevent crashes in _elementtree due to unsafe cleanup of Element.text and Element.tail (GH-3924) (#3950)

Also remove an obsolete note about
backward compat with old Pythons.

Add a new _testcapi._read_null() function to crash Python in a
reliable way on s390x.

On s390x, ctypes.string_at(0) returns an empty string rather than
crashing.