Fixed audio port handling when the same slot needs to be reconnected

Ignore-this: 8e925de243083b5898b0f33e9cdc1be5

darcs-hash:20100316131918-1e3d8-f990f544c89a1a64a0bbb213be6b94559b8cf2fc
Fixed handling of Reason header in Invitation

Ignore-this: f0965006cdd6c5faead2b11601b1ab2b

darcs-hash:20100317115214-1e3d8-a74b1378c5252f10b69bb37e833afe4ba39d1557