Fixed sipsimple.cpim to use RFC3339 rather than ISO8601 timestamps

Ignore-this: beb817a4b2f20106cbfd487a0033c7b8

darcs-hash:20100119110401-1e3d8-ab7b6c2d63b32dfedd41de7abd8bb1aefeb1cccc
Improved threading code's readability in sipsimple.clients

Ignore-this: d086d5fa814d05beba3b1cd2563bbf6f

darcs-hash:20100119110421-1e3d8-7dff2806021e45053f76cf9a4585f5a68b15da86