This is the first swath of changes, replacing add_undo with MementoCommand
pattern, through most of the editor_mouse.cc file. However there were a few
places that weren't symmetrical that I need to think about. The question is
whether to tweak things so that they are symmetrical (add_undo paired with
add_redo*), or to allow Commands to not be undoable or not be redoable. Your
thoughts are welcome.
git-svn-id: svn://localhost/ardour2/branches/undo@685 d708f5d6-7413-0410-9779-e7cbd77b26cf
55159005b9