Add support for ICE keepalive

Ignore-this: 3908bdd545fee54184f396275eafb552

darcs-hash:20100406174341-56b4d-669375d24a13b682d14f698529e8137a5a62a6f7
Use default username as display name for Bonjour if it was set to empty

Ignore-this: 3df6f13df6510d3a92554e07f3e4e370

darcs-hash:20100408080722-56b4d-d3a8f527fc370bf2186e51063ba86dec49f0fb82