Test new RooLinkedList::At implementation #16
Description
In the linked_list_at branch, I added a vector to the linked list that keeps track of the pointers in the list, so that ::At can be a lot faster. It seems like ::At is in fact used quite a lot in things like HistFactory. In one of the workspaces from @vincecr0ft, I measured a speed-up of a factor 1.6.
We should test this further on different types of workspaces to make sure it does not cause performance regressions. If it does, we could decide whether to keep it in, but with an (de)activation switch or whether to discard it completely.
If we keep it in, we should release it to upstream (other issue).