Remove dead/annoying/unsafe code

Note the old Note::operator= was unsafe, since it made shallow copies of the on
and off events, which results in a double delete of events when the notes are
destructed.

libs/evoral/src/Control.cpp

@@ -18,8 +18,6 @@
 
 #include <iostream>
 
-#include "pbd/stacktrace.h"
-
 #include "evoral/Control.hpp"
 #include "evoral/ControlList.hpp"
 #include "evoral/ParameterDescriptor.hpp"