Use SIPURI class in Invitation to copy request URI to Contact header on incoming INVITE

darcs-hash:20090126123334-58103-347a19966058b74273bf4c88a020753c02d7c34b
enginebuffer: work well with the latest changes in pypjua

darcs-hash:20090126130240-b2873-6a184ceb6e6a314c6cca6933df8c7927f536052b