session2: add __all__

darcs-hash:20090416124020-b2873-a5d069289d684bf7d2f62b263c7e3c0e7cd82492
Added old default account in SIPAccountManagerDidChangeDefaultAccount

Ignore-this: e24d0146fa1cdf12435d9b70862e2990

darcs-hash:20090416130222-1e3d8-55b44a4d34b796236b23cb0620c529581aad393e