@update
<> Now, the tracer have it own world (a copy of gint world), so this allows the
tracer to be completely independent vis-à-vis the traced world. The world can
be analyzed with a menu (not implemented but noted in the TODO)
@add
* callgraph: add menu
* callgraph: Generate the callgraph even if a breakpoint has been placed after a subroutine.
@fix
* disable the UBC when we are in the "user" handler (more stability)
* the key [EXE] has been mapped by the GUI and exit the handler when pressed.