Added dev-php/libvirt-php-0.4.6-r1 with patch for virDomainMigrateToURI2()

The libvirt function virDomainMigrateToURI2() was not yet implemented in php-libvirt.
I added it as libvirt_domain_migrate_to_uri2(), using the existing function libvirt_domain_migrate_to_uri() as base and this definition:
http://libvirt.org/html/libvirt-libvirt.html#virDomainMigrateToURI2

Needs testing, then the patch can be pushed upstream.