We must not access memory outside of the allocated buffer.

variant objects have no (declared) properties, so the `get_properties`
handlers returns a pointer to constant storage for efficiency reasons.
This pointer must not be returned from the `get_gc` handler, though;
instead we set up an own `get_gc` handler and return NULL from it, to
signal that there are no properties to collect.

* PHP-7.3:
  Fix #78090: bug45161.phpt takes forever to finish

Not all systems support the discard protocol (TCP port 9), and since
there is no particular reason to use it, we switch to using actual
server testing.

* 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.

Mostly reindent PHP scripts to spaces.

* PHP-7.3:
  Relax test expectation