tree mode: improve ev_pickup event generation

[thiell]

ev_pickup in tree mode in 1.8 could need some improvements, right now it is blindly called after ev_start(). But it might be difficult to detect when commands really start. TBD.

[degremont]

But it might be difficult to detect when commands really start.

If we are aware of start event, could not we use the same mechanism to be aware of pickup event?
What about ev_hup? Could we copy this?