Added new core objects to sipsimpe.core.__all__

Ignore-this: 136d0e91b3deafed7a78be47bfa06995

darcs-hash:20090625111755-1e3d8-b778487b451299dd3bbf749e7cc24f24b82ef692
Added sending of DNSLookupTrace notifications in sipsimple.lookup

Ignore-this: d9309a2b63b20d3333cc471f5f74dd09

darcs-hash:20090626145912-1e3d8-afad41e6fc61d04a9442b8b38f91a032346b0307