Make it a std::vector that reserves enough space based on the number of
functions in the initial bottom-up ordering.
This is the first step in making it possible for function passes to
notify the pass manager of new functions to process.
Make it a bit more clear that we're alternating between collecting (and
then running) function passes, and running module passes. Removes some
duplication that was present.
Reapplies 9d4d3c8 with fixes for bisecting pass execution.
(Headers first)
It has been generally agreed that we need to do this reorg, and now
seems like the perfect time. Some major pass reorganization is in the
works.
This does not have to be the final word on the matter. The consensus
among those working on the code is that it's much better than what we
had and a better starting point for future bike shedding.
Note that the previous organization was designed to allow separate
analysis and optimization libraries. It turns out this is an
artificial distinction and not an important goal.
