* libguile/continuations.c (scm_i_continuation_to_frame):
* libguile/stacks.c (scm_make_stack):
* libguile/vm.c (scm_i_vm_cont_to_frame, scm_i_vm_capture_stack):
  (vm_return_to_continuation_inner)
  (struct vm_reinstate_partial_continuation_data):
  (vm_reinstate_partial_continuation_inner):
  (vm_reinstate_partial_continuation):
* libguile/vm.h (sstruct scm_vm_cont): Simplify VM continuations by
  recording the top FP by offset, not value + reloc.
* libguile/frames.c (frame_offset, scm_i_vm_frame_offset): Remove unused
  functions.
* libguile/frames.h (SCM_VALIDATE_VM_FRAME, scm_i_vm_frame_offset):
  Remove.
* libguile/control.c (reify_partial_continuation): Once we know the
  base_fp, relocate the dynamic stack.
* libguile/dynstack.h:
* libguile/dynstack.c (scm_dynstack_relocate_prompts): New function.
  (scm_dynstack_wind_prompt): Adapt to add new fp offset.