Revert "Disable IPv6 in Net::LDAP. bugid:111222" bugid:111628

This reverts commit 54d0339909b342743529f58d91d0085752968f9a.

Conflicts:
	lib/MT.pm
Revert "Add Sub::Uplevel to extlib for constant::override. bugid:111222" bugid:111628

This reverts commit 78e2846a1762d165948316951ef775e28e341aaf.