* PHP-7.1:
  Add support for getting SKIP_TAGSTART and SKIP_WHITE options

When `XML_OPTION_SKIP_TAGSTART` and `XML_OPTION_SKIP_WHITE` had been
introduced[1], it had been overlooked to also support them for
`xml_parser_get_option()`.  We catch up on that.

[1] <http://git.php.net/?p=php-src.git;a=commit;h=b57dc275950b228f2399990471c4f22b7d154c6c>

* PHP-7.1:
  Fix #30875: xml_parse_into_struct() does not resolve entities

Setting up an empty default handler is not only useless, but actually
harmful, since internal entity-references are not resolved anymore.
From the libexpat docs[1]:

| Setting the handler with this call has the side effect of
| turning off expansion of references to internally defined general
| entities. Instead these references are passed to the default
| handler.

[1] <https://www.xml.com/pub/1999/09/expat/reference.html#setdefhandler>