Replace ($var sym) with ($values (sym)).

* module/language/cps.scm: Remove $var.  Replaced by $values with one
  value.

* module/language/cps/arities.scm:
* module/language/cps/closure-conversion.scm:
* module/language/cps/compile-rtl.scm:
* module/language/cps/dfg.scm:
* module/language/cps/slot-allocation.scm:
* module/language/cps/verify.scm:
* module/language/tree-il/compile-cps.scm: Adapt all the world.
Rewrite slot allocation pass

* module/language/cps/slot-allocation.scm ($allocation): Refactor
  internal format of allocations.  Instead of an allocation being a hash
  table of small $allocation objects, it is an $allocation object that
  contains packed vectors.
  (find-first-trailing-zero): Rework to not need a maximum.
  (lookup-maybe-slot): New interface.
  (lookup-slot): Raise an error if a var has no slot.
  (lookup-call-allocation): New helper.
  (lookup-constant-value, lookup-maybe-constant-value):
  (lookup-call-proc-slot, lookup-parallel-moves): Adapt to $allocation
  change

  (allocate-slots): Rewrite so that instead of being recursive, it
  traverses the blocks in CFA order.  Also, procedure call frames are
  now allocated with respect to the live set after using arguments (and
  killing any dead-after-use vars); this should make call frames more
  compact but it does necessitate a parallel move solution.  Therefore
  parallel moves are recorded for all calls, for arguments; also if the
  continuation is a $ktrunc, the continuation gets parallel moves for
  the results.

  This rewrite is in preparation to allocating call args directly in the
  appropriate slots, where possible.

* module/language/cps/compile-rtl.scm (compile-fun): Adapt to slot
  allocation changes, using lookup-maybe-slot where appropriate,
  performing parallel moves when calling functions, and expecting return
  moves to be associated with $ktrunc continuations.
Try to allocate arguments directly in call frames

* module/language/cps/slot-allocation.scm (allocate-slots): Convert
  cont-table to a vector, for ease of access.  Run a pass before
  allocation that determines the set of variables whose slot allocation
  can and should be delayed, so that they can ideally be allocated
  directly in an argument slot.
Remove MVRA accessors in libguile

* libguile/vm.c (scm_i_vm_capture_stack): Remove MVRA argument, in
  preparation for removing MVRA from frames.
  (scm_i_capture_current_stack): Adapt to scm_i_vm_capture_stack
  change.
  (vm_reinstate_partial_continuation): Remove references to MVRA.

* libguile/vm.h (struct scm_vm_cont): Remove mvra member.

* libguile/vm-engine.c (call): Set MVRA to 0.  Will remove later.
  (return-values): Return to RA.
  (call/cc): Remove MVRA from capture call.

* libguile/frames.c:
* libguile/frames.h (SCM_FRAME_MV_RETURN_ADDRESS)
  (SCM_FRAME_RTL_MV_RETURN_ADDRESS, scm_frame_mv_return_address): Remove
  accessors.

* libguile/control.c (reify_partial_continuation): Adapt to
  scm_i_vm_capture_stack change.
Remove MVRA from VM frames

* libguile/_scm.h (SCM_OBJCODE_MINOR_VERSION): Bump for frame layout
  change.

* libguile/frames.c: Update some static checks.
  (scm_frame_num_locals, scm_frame_local_ref, scm_frame_local_set_x):
  Update to not skip over uninitialized frames, as that's not a thing
  any more.

* libguile/frames.h: Update to remove MVRA.  Woo!

* libguile/vm-engine.c (ALLOC_FRAME, RETURN_ONE_VALUE):
  (rtl_vm_engine): Update for 3 words per frame instead of 4.

* libguile/vm.c (vm_return_to_continuation): Likewise.

* module/language/cps/slot-allocation.scm (allocate-slots): 3 words per
  frame, not 4.

* module/system/vm/assembler.scm (*bytecode-minor-version*): Bump.  Also
  remove a couple of tc7's that aren't around any more.
Remove use of SCM_CRITICAL_SECTION in smob.c

* libguile/smob.c (scm_make_smob_type): Use a mutex instead of a
  critical section, which does an async tick.  Not important, just a
  thing I saw.
Frame pointer points to local 0 instead of local 1

* libguile/frames.h: Change so that fp points at local 0 instead of
  local 1, and clean up a bit.
  (struct scm_vm_frame): Remove program, and rename stack to locals.
  (SCM_FRAME_DATA_ADDRESS): Remove; it was redundant with
  SCM_FRAME_LOWER_ADDRESS.
  (SCM_FRAME_STACK_ADDRESS): Remove; replace with the new
  SCM_FRAME_LOCALS_ADDRESS.
  (SCM_FRAME_UPPER_ADDRESS): Remove; unused.
  (SCM_FRAME_NUM_LOCALS, SCM_FRAME_PREVIOUS_SP): New defines.
  (SCM_FRAME_BYTE_CAST, SCM_FRAME_STACK_CAST): Remove; unused;
  (SCM_FRAME_LOCAL): New define, replaces SCM_FRAME_VARIABLE.
  (SCM_FRAME_PROGRAM): Add cautionary commentary.

* libguile/frames.c: Adapt static asserts.
  (scm_frame_num_locals, scm_frame_local_ref, scm_frame_local_set_x):
  Adapt.  This means that frame-local-ref 0 now returns the procedure.

* libguile/vm-engine.c (ALLOC_FRAME, RESET_FRAME)
  (FRAME_LOCALS_COUNT, LOCAL_REF, LOCAL_SET, RETURN_VALUE_LIST): Adapt
  to change in fp.
  (LOCAL_ADDRESS): New helper.
  (POP_CONTINUATION_HOOK): Reimplement, taking the previous FP as an
  argument.
  (ABORT_CONTINUATION_HOOK): Reimplement, taking no arguments.
  (RETURN_ONE_VALUE): Reimplement.
  (RETURN_VALUE_LIST): Adapt to FP change.
  (halt, return-values, subr-call, foreign-call, prompt)
  (continuation-call, compose-continuation, call/cc, abort): Adapt to FP
  change, mostly via using LOCAL_ADDRESS, etc abstractions instead of
  using the raw frame pointer.

* libguile/control.c (reify_partial_continuation): Update for fp
  change.

* libguile/vm.c (vm_reinstate_partial_continuation): Adapt to removal of
  SCM_FRAME_UPPER_ADDRESS.

* module/system/vm/frame.scm (frame-call-representation): Adapt to
  frame-local-ref change.

* module/system/vm/trace.scm (print-return): Remove unused
  frame-num-locals call.
All instruction pointers are now scm_t_uint32*

* libguile/frames.h (SCM_FRAME_RTL_RETURN_ADDRESS)
  (SCM_FRAME_SET_RTL_RETURN_ADDRESS): Remove.  The variants without _RTL
  now work fine.
  (struct scm_vm_frame): Change the return address to be a
  scm_t_uint32*.
  (struct scm_frame): Change IP to be scm_t_uint32*.

* libguile/frames.c (scm_c_make_frame)
* libguile/control.c (reify_partial_continuation, scm_c_abort)
* libguile/dynstack.c (PROMPT_IP)
  (scm_dynstack_push_prompt, scm_dynstack_find_prompt)
* libguile/dynstack.h:
* libguile/vm-engine.c (SYNC_IP, RETURN_ONE_VALUE)
  (call, return-values, prompt): Adapt.
Rename scm_tc7_rtl_program to scm_tc7_program

* libguile/tags.h (scm_tc7_program): Rename from scm_tc7_rtl_program.
* libguile/continuations.c:
* libguile/control.c:
* libguile/evalext.c:
* libguile/foreign.c:
* libguile/goops.c:
* libguile/gsubr.c:
* libguile/print.c:
* libguile/programs.c:
* libguile/programs.h:
* libguile/vm-engine.c: Adapt users.

* module/system/vm/assembler.scm: Rename a tc7-rtl-program local to
  tc7-program.
* libguile/tags.h (scm_tc7_program): Rename from scm_tc7_rtl_program. * libguile/continuations.c: * libguile/control.c: * libguile/evalext.c: * libguile/foreign.c: * libguile/goops.c: * libguile/gsubr.c: * libguile/print.c: * libguile/programs.c: * libguile/programs.h: * libguile/vm-engine.c: Adapt users.

* module/system/vm/assembler.scm: Rename a tc7-rtl-program local to
  tc7-program.
Remove RTL_ infix from macros

* libguile/programs.h (SCM_PROGRAM_P):
  (SCM_PROGRAM_CODE):
  (SCM_PROGRAM_FREE_VARIABLES):
  (SCM_PROGRAM_FREE_VARIABLE_REF):
  (SCM_PROGRAM_FREE_VARIABLE_SET):
  (SCM_PROGRAM_NUM_FREE_VARIABLES):
  (SCM_VALIDATE_PROGRAM): Remove RTL_ infix.

* libguile/continuations.c:
* libguile/continuations.h:
* libguile/control.c:
* libguile/foreign.c:
* libguile/frames.c:
* libguile/gsubr.c:
* libguile/gsubr.h:
* libguile/procprop.c:
* libguile/procs.c:
* libguile/programs.c:
* libguile/stacks.c:
* libguile/vm-engine.c: Adapt.
scm_i_make_rtl_program in BUILDING_LIBGUILE

* libguile/programs.h (scm_i_make_rtl_program): Enclose in a
  BUILDING_LIBGUILE guard.
scm_i_rtl_program_* -> scm_i_program_*

* libguile/programs.h (scm_i_make_program):
* libguile/programs.c (scm_i_program_name):
  (scm_i_program_documentation):
  (scm_i_program_properties): Remove "rtl_" infix.

* libguile/objcodes.c:
* libguile/procprop.c:
* libguile/vm.c: Adapt callers.
Remove make-rtl-program.

* libguile/programs.h:
* libguile/programs.c (scm_make_rtl_program): Remove.  Unused.

* module/system/vm/program.scm (system): Remove make-rtl-program
  export.  Unused.
rtl-program? -> program?

* libguile/programs.c (scm_program_p): Rename from scm_rtl_program_p.
  Changes name also from rtl-program? to program?.

* libguile/programs.h:
* module/ice-9/session.scm:
* module/language/tree-il/analyze.scm:
* module/statprof.scm:
* module/system/repl/command.scm:
* module/system/repl/debug.scm:
* module/system/vm/coverage.scm:
* module/system/vm/disassembler.scm:
* module/system/vm/frame.scm:
* module/system/vm/program.scm:
* module/system/vm/traps.scm:
* module/system/xref.scm: Adapt.
rtl-program-code -> program-code

* libguile/programs.h:
* libguile/programs.c (scm_program_code): Rename from
  scm_rtl_program_code.  Also renames rtl-program-code to program-code.

* module/statprof.scm:
* module/system/repl/command.scm:
* module/system/repl/debug.scm:
* module/system/vm/coverage.scm:
* module/system/vm/disassembler.scm:
* module/system/vm/program.scm:
* module/system/vm/traps.scm:
* test-suite/tests/dwarf.test:
* test-suite/tests/rtl.test: Adapt callers.
Reorganize programs.h.

* libguile/programs.h: Reorganize.
Remove unused C scm_program_source.

* libguile/programs.c (scm_program_source): Remove; not called.  (The
  definition is in Scheme.)
Rename (system vm program) internal functions to remove rtl-

* module/system/vm/program.scm (program-name)
  (program-documentation): Rename (removing rtl-).
* libguile/programs.c (scm_i_program_name):
  (scm_i_program_documentation): Adapt callers.
Rename internals of (system vm program) program-minimum-arity

* module/system/vm/debug.scm (find-program-minimum-arity): Rename from
  program-minimum-arity.

* module/system/vm/program.scm (program-minimum-arity): Rename from
  rtl-program-minimum-arity.

* libguile/programs.c (scm_i_program_arity): Adapt.
Excise "rtl-" from fallback program printer

* libguile/programs.c (scm_i_program_print): Fallback printer uses
  "program", not "rtl-program".