Added frozen and non-frozen types for SDP related classes

Ignore-this: afd3af2a8558930c84e921002a3a7dd6

darcs-hash:20090616094636-1e3d8-d253a5c295b9746d646f5822d8f09609a648a4c0
Added module with SIP headers types

Ignore-this: 450b4e10289398ab61ff0663c79472b

darcs-hash:20090616094738-1e3d8-46ec1cd35c589927e8b1e665960ca94ef4d93dd0