stringstream: cleanup

src/client/videomanager.cpp

src/connectivity/connectionmanager.cpp

src/jamidht/conversationrepository.cpp

src/jamidht/namedirectory.cpp

src/media/media_encoder.cpp

src/media/media_encoder.h

src/media/media_filter.cpp

src/media/media_recorder.cpp

src/sip/sdp.cpp