Merge branch 'master' into windows

diff --cc gtk2_ardour/midi_tracer.cc
Simple merge

diff --cc gtk2_ardour/port_matrix.cc
Simple merge

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

diff --cc libs/ardour/lv2_plugin.cc
Simple merge

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

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

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

diff --cc libs/pbd/wscript
Simple merge