Generate class entries from stubs for com, standard, xmlreader, xmlwriter, xsl, zip, Zend

Closes GH-6706

Fix COMPersistHelper::__construct() stub

`$variant` is optional.

Update ext/com_dotnet parameter names

Closes GH-6296.

Autogenerate function entries for COMPersistHelper

Co-authored-by: Nikita Popov <nikita.ppv@googlemail.com>

Generate method entries from stubs for a couple of extensions

Closes GH-5368

Add stubs for COMPersistHelper