Run integration tests also with PHP 7.4.

Prevent unescaping of apostrophe and quote entities in XML response.

Properly handle address-related errors by expecting socket.gaierror i…

…nstead of errno code.

In case of unresolvable hostname or IPv6 address specified as 'host' setting.
It would throw completely different errno on Linux (-2) or Windows (11004), when expecting errno (8).

Package update:

Fixed: Double escaped response data when using SimpleXMLTreeBuilder. (fix #81)
Fixed: Did not properly detect whether 'max_children', 'max_data' or 'max_depth' is a valid number. (fix #59, fix #66)