Pack array dimensions in array object

Pack array dimensions in array object

* libguile/arrays.c (scm_i_make_array): redo object layout.

* libguile/arrays.h (SCM_I_ARRAY_V, SCM_ARRAY_BASE, SCM_I_ARRAY_DIMS):
  to match new layout.

  (SCM_I_ARRAY_SET_V, SCM_ARRAY_SET_BASE): new setters.

  (SCM_I_ARRAY_MEM, scm_i_t_array): unused, remove.

  (scm_i_shap2ra, scm_make_typed_array, scm_from_contiguous_typed_array,
  scm_from_contiguous_array, scm_make_shared_array, scm_transpose_array,
  scm_array_contents): fix uses of SCM_I_ARRAY_V, SCM_ARRAY_BASE as
  lvalues.

* libguile/array-map.c (make1array, scm_ramapc): fix uses of
  SCM_I_ARRAY_V, SCM_ARRAY_BASE as lvalues.