Don't fail a service lookup if an IP address is provided

Ignore-this: cf4fd2a3bb9bbf2f76feb649067d164e

darcs-hash:20100531085402-56b4d-d10676b0e21f0eab3d9b6b9bd60528ca770938b6
Add NAT detector to SIPApplication object

Ignore-this: 50c097b2e6b5ed8923ada39bfa427c2d

darcs-hash:20100615105318-56b4d-ac28f9f25ea958cf0a29b4461bc1669f1f5835b1