Better Valgrind 3.6.0 compatibility

* add new default known event types: LLx (last level), branch prediction, global bus event
* the known types are not only used at first run
* derived types are shown even if just one referenced event type is provided in profile.
E.g. for "Ev = A + B", Ev is already shown if just events for A or for B are provided.
Previously, events for both A and B had to be provided.
To have "CEst" work with both L2 (< VG 3.6) and LL (VG 3.6) event types, this change is needed:
"CEst" (Cycle estimation) now references both L2 and LL events.
* For the formula of derived event types, the displayed formula is cut down to only reference existing types.
For editing,
the full formula is used.