* PHP-7.3:
  Fix #79191: Error in SoapClient ctor disables DOMDocument::save()

The culprit is the too restrictive fix for bug #71536, which prevents
`php_libxml_streams_IO_write()` from properly executing when unclean
shutdown is flagged.  A *more* suitable solution is to move the
`xmlwriter_free_resource_ptr()` call from the `free_obj` handler to an
added `dtor_obj` handler, to avoid to write to a closed stream in case
of late object freeing.  This makes the `EG(active)` guard superfluous.

We also fix bug79029.phpt which has to use different variables for the
three parts to actually check the original shutdown issue.

Thanks to bwoebi and daverandom for helping to investigate this issue.

While basic support for MSVCRT debugging has been added long
ago[1], the leak checking is not usable for the test suite, because we
are no longer calling `xmlCleanupParser()` on RSHUTDOWN of
ext/libxml[2], and therefore a few bogus leaks are reported whenever
ext/libxml is unloaded.

We therefore ignore memory leaks for this case.  We introduce
`ZEND_IGNORE_LEAKS_BEGIN()` and `ZEND_IGNORE_LEAKS_END()` to keep
those ignores better readable, and also because these *might* be
useful for other leak checkers as well.

We also explicitly free the `zend_handlers_table` and the `p5s` to
avoid spurious leak reports.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=d756e1db2324c1f4ab6f9b52e329959ce6a02bc3>
[2] <http://git.php.net/?p=php-src.git;a=commit;h=8742276eb3905eb97a585417000c7b8df85006d4>

We backport the fix PHP 7.3, since this branch is affected as well.

(cherry picked from commit b5e004379647bd1ebb75eb2eac8826fb6abdd3d8)
(cherry picked from commit e36daa6927c05d2e687bb77495ef206cde118b33)
(cherry picked from commit 2704ee6844c03348de9d15e74646d09007ef0f7c)

This reverts commit d8ad2f4695ebd6dc2d4e668d9baeac1c071791a6.

* PHP-7.3:
  Fix test to be skipped if dom is not available

* PHP-7.2:
  Fix test to be skipped if dom is not available