Merge branch 'sip_dev' into stable

src/account.h

src/global.h

src/iaxaccount.cpp

src/iaxaccount.h

src/iaxvoiplink.cpp

src/iaxvoiplink.h

src/managerimpl.cpp

src/managerimpl.h

src/sipaccount.cpp

src/sipaccount.h

src/sipvoiplink.cpp

src/sipvoiplink.h

src/useragent.cpp

src/useragent.h

src/voiplink.h