runtime and debugging support for callee-parsed procedure args

runtime and debugging support for callee-parsed procedure args

* libguile/objcodes.h: Bump for metadata format change.

* libguile/frames.h: Rework so we don't frob the program's nargs, nlocs,
  etc at runtime. Instead we don't really know what's a local var, an
  argument, or an intermediate value. It's a little unfortunate, but
  this will allow for case-lambda, and eventually for good polymorphic
  generic dispatch; and the nlocs etc can be heuristically
  reconstructed. Such a reconstruction would be better done at the
  Scheme level, though.
  (SCM_FRAME_STACK_ADDRESS): New macro, the pointer to the base of the
  stack elements (not counting the program).
  (SCM_FRAME_UPPER_ADDRESS): Repurpose to be the address of the last
  element in the bookkeeping part of the stack -- i.e. to point to the
  return address.

* libguile/vm-engine.h:
* libguile/vm-i-system.c: Adapt to removal of stack_base. Though we
  still detect stack-smashing underflow, we don't do so as precisely as
  we did before, because now we only detect overwriting of the frame
  metadata.

* libguile/vm-engine.c (vm_engine): Remove the stack_base variable. It
  is unnecessary, and difficult to keep track of in the face of
  case-lambda. Also fix miscommented "ra" and "mvra" pushes. Push the
  vp->ip as the first ra...
* libguile/vm-i-system.c (halt): ...because here we can restore the
  vp->ip instead of setting ip to 0. Allows us to introspect ips all
  down the stack, including in recursive VM invocations.

* libguile/frames.h:
* libguile/frames.c (scm_vm_frame_stack): Removed, because it's getting
  more difficult to tell what's an argument and what's a temporary stack
  element.
  (scm_vm_frame_num_locals): New accessor.
  (scm_vm_frame_instruction_pointer): New accessor.
  (scm_vm_frame_arguments): Defer to an implementation in Scheme.
  (scm_vm_frame_num_locals scm_vm_frame_local_ref)
  (scm_vm_frame_local_set_x): Since we can get not-yet-active frames on
  the stack now, with our current calling convention, we have to add a
  heuristic here to jump over those frames -- because frames have
  pointers in them, not Scheme values.

* libguile/programs.h:
* libguile/programs.c (scm_program_arity): Remove, in favor of..
  (scm_program_arities): ...this, which a list of arities, in a new
  format, occupying a slot in the metadata.

* module/language/assembly/decompile-bytecode.scm (decode-load-program):
  Fix mv-call decompilation.

* module/system/vm/frame.scm (vm-frame-bindings, vm-frame-binding-ref)
  (vm-frame-binding-set!): New functions, to access bindings by name in
  a frame.
  (vm-frame-arguments): Function now implemented in Scheme. Commented
  fairly extensively.

* module/system/vm/program.scm (program-bindings-by-index)
  (program-bindings-for-ip): New accessors, parsing the program bindings
  metadata into something more useful.
  (program-arities, program-arguments): In a case-lambda world, we have
  to assume that programs can have multiple arities. But it's tough to
  detect this algorithmically; instead we're going to require that the
  program metadata include information about the arities, and the parts
  of the program that that metadata applies to.
  (program-lambda-list): New accessor.
  (write-program): Show multiple arities.

* module/language/glil/compile-assembly.scm (glil->assembly): Add
  "arities" to the state of the compiler, and add arities entries as
  appropriate.