Rewrite effects analysis to be precise for fields.

Rewrite effects analysis to be precise for fields.

* module/language/cps/effects-analysis.scm: Rewrite so that instead of
  the depends/causes effects, there is just &type-check, &allocation,
  &read, and &write.  The object kind is a separate part of the
  bitfield, and the field in the object (if appropriate) is another
  field.  Effects are still a fixnum.  This enables precise effects for
  vectors and structs on all architectures.

  This kind of effects analysis was not possible in Tree-IL because
  Tree-IL relied on logior-ing effects of subexpressions, whereas with
  CPS we have no sub-expressions and we do flow analysis instead.

  (effect-clobbers?): Replace effects-commute? with this inherently
  directional and precise predicate.

* module/language/cps/cse.scm (compute-always-available-expressions):
  (compute-equivalent-subexpressions): Adapt to effects analysis
  change.
* module/language/cps/dce.scm (compute-live-code): Likewise.