[#5168] Fix dynamic/static codec payload type ambiguity

sflphone-common/src/audio/audiortp/AudioRtpSession.cpp

sflphone-common/src/audio/codecs/Makefile.am

sflphone-common/src/audio/codecs/alaw.cpp

sflphone-common/src/audio/codecs/audiocodec.h

sflphone-common/src/audio/codecs/celtcodec.cpp

sflphone-common/src/audio/codecs/g722.cpp

sflphone-common/src/audio/codecs/gsmcodec.cpp

sflphone-common/src/audio/codecs/speexcodec_nb.cpp

sflphone-common/src/audio/codecs/speexcodec_ub.cpp

sflphone-common/src/audio/codecs/speexcodec_wb.cpp

sflphone-common/src/audio/codecs/ulaw.cpp