Record transformation time

When developping in Why3, one might want to quickly know which part of the replay of a file takes time. To this end, I think it would be useful if the transformations also recorded the time they spend. It could be stored in the why3session.xml with another attribute to the transformation, which would give something like <transf name="split_vc" time="0.01" >. It probably should be disabled by default, although it would mean that we should be able to handle session files that differ in this way.

As for prover calls, it could also be shown in the IDE. To not clutter the IDE, it could only be shown if the time goes beyond X seconds.

Would it even make sense to do this ? Is the time spent by transformations too volatile ?