Add auxiliary definitions for boxes

* module/language/cps/cse.scm (compute-equivalent-subexpressions): Add
  auxiliary definitions for boxes.
Set-car! on a dead pair does not force the pair to be live

* module/language/cps/dce.scm (constant-type, lookup-type)
  (default-type-checker, *primcall-type-checkers*)
  (define-primcall-type-checker, define-simple-primcall-types)
  (check-primcall-arg-types): Define a really lame type analysis that
  can elide some expressions causing &type-check.
  (compute-live-code): Wire up the type checker.
frame-call-representation has #:top-frame? as keyword argument

* module/system/vm/frame.scm (frame-call-representation): Change
  top-frame? argument to be a keyword instead of an optional argument.

* module/system/vm/trace.scm (print-application): Adapt caller.
frame-address, frame-stack-pointer return offsets

* libguile/frames.c (scm_frame_address, scm_frame_stack_pointer): Return
  offsets instead of absolute pointers.  This is robust in the presence
  of stack relocation.

* module/system/repl/debug.scm (print-registers): Adapt to print sp and
  fp as integers.
Refactorings to apply-hook and push-continuation-hook

* libguile/vm-engine.c (vm_engine): Always invoke the apply hook after
  the ip has been reset.  Avoids problems in frame-bindings, which
  builds its bindings map based on the IP.  Invoke push-continuation
  before linking the new frame, so that more locals are available to the
  frame inspector.

* module/system/vm/traps.scm (trap-in-procedure): No need for a
  push-cont handler, as the apply handler will exit the frame.
Program printing tweaks

* module/system/vm/program.scm (print-program): New public interface --
  the guts of write-program, but refactored to be able to work when only
  given an addr.
  (write-program): Use print-program.

* module/system/vm/frame.scm (frame-call-representation): Remove attempt
  to abbreviate procedure representations; was confusing because the
  result would write as a string, quotes and all.
Fix frame-call-representation for frames from apply-hook

* module/system/vm/frame.scm (frame-call-representation): Fix when
  called on frames that are created from the apply hook.
Fix thinko in synthesize-definition-effects!

* module/language/cps/effects-analysis.scm (synthesize-definition-effects!):
  Fix a boneheaded thinko that caused all primcalls to be marked as
  causing car, cdr, vector, struct, and box effects.
Synthetic definitions take advantage of CSE'd vars

* module/language/cps/cse.scm (compute-available-expressions):
  Simplify initialization.
  (compute-equivalent-subexpressions): When synthesizing definitions,
  use substed vars.  Add synthetic definitions after processing an
  expression, to take advantage of the substed vars.
Add dump-dfg pretty-printer

* module/language/cps/dfg.scm (dump-dfg): New pretty-printer.  Under
  construction.
CSE effects analysis cleanup

* module/language/cps/cse.scm (compute-always-available-expressions):
  Use constant? instead of zero?, to avoid punching through the effects
  abstraction.
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.
Add syntax-parameterize indentation to .dir-locals.el.

* .dir-locals.el: Add syntax-parameterize indentation.