I've been playing around with removing the legacy VRP code for the
next release.  It's a layered onion to get this right, but the first
bit is pretty straightforward and may be useful for this release.
Basically, it entails removing the old VRP pass itself, along with
value_range_equiv which have no producers left.  The current users of
value_range_equiv don't put anything in the equivalence bitmaps, so
they're basically behaving like plain value_range.

I removed as much as possible without having to change any behavior,
and this is what I came up with.  Is this something that would be
useful for this release?  Would it help release managers have less
unused cruft in the tree?

Neither Andrew nor I have any strong feelings here.  We don't foresee
the legacy code changing at all in the offseason, so we can just
accumulate these patches in local trees.

Thoughts?
Aldy