Merge branch 'master' into windows

diff --cc gtk2_ardour/ardour_ui.cc
Simple merge

diff --cc gtk2_ardour/editor_videotimeline.cc
Simple merge

diff --cc gtk2_ardour/export_video_dialog.cc
Simple merge

diff --cc gtk2_ardour/utils.cc
Simple merge

diff --cc libs/ardour/ardour/session.h
Simple merge

diff --cc libs/ardour/audioengine.cc
Simple merge

diff --cc libs/ardour/port.cc
Simple merge

diff --cc libs/ardour/session.cc
Simple merge

diff --cc libs/ardour/session_state.cc
Simple merge