Give arrays a proper type in C land

As long as we have a tc7 for arrays, we should be able to access it with
a struct type instead of casting each word.

* libguile/arrays-internal.h: New file.
* libguile/arrays.h (scm_array_p): Take just one argument.
(SCM_I_ARRAYP):
(SCM_I_ARRAY_NDIM):
(SCM_I_ARRAY_V):
(SCM_I_ARRAY_BASE):
(SCM_I_ARRAY_DIMS):
(SCM_I_ARRAY_SET_V):
(SCM_I_ARRAY_SET_BASE): Remove.
(scm_i_raw_array, scm_i_make_array, scm_i_shap2ra, scm_init_arrays):
Remove internally-linked decls.
* libguile/init.c:
* libguile/print.c:
* libguile/array-handle.c: Use interfaces from new file.
* module/system/vm/assembler.scm: Update, as we now shift the dimension
count by only 16.  Requires a rebuild!

libguile/arrays-internal.h

@@ -0,0 +1,86 @@
+#ifndef SCM_ARRAYS_INTERNAL_H
+#define SCM_ARRAYS_INTERNAL_H
+
+/* Copyright 1995-1997,1999-2001,2004,2006,2008-2010,2012,2018,2025
+     Free Software Foundation, Inc.
+
+   This file is part of Guile.
+
+   Guile is free software: you can redistribute it and/or modify it
+   under the terms of the GNU Lesser General Public License as published
+   by the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   Guile is distributed in the hope that it will be useful, but WITHOUT
+   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+   FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
+   License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with Guile.  If not, see
+   <https://www.gnu.org/licenses/>.  */
+
+
+
+#include "libguile/arrays.h"
+
+
+
+struct scm_array
+{
+  scm_t_bits tag_and_ndims;
+  SCM vector;
+  size_t base;
+  struct scm_t_array_dim dims[];
+};
+
+/* There is a naming confusion: scm_is_array exists and is used for
+   generalized arrays, allowing e.g. (array? #(1 2 3)) to be true.  Here
+   we are concerned with proper multidimensional arrays, which are their
+   own data type.  Mostly we can use this "struct scm_array" as a way to
+   avoid confusion, but we have to name this function
+   "scm_is_tagged_array" instead of "scm_is_array" as we would like.  */
+static inline int
+scm_is_tagged_array (SCM x)
+{
+  return SCM_HAS_TYP7 (x, scm_tc7_array);
+}
+
+static inline struct scm_array*
+scm_to_array (SCM x)
+{
+  if (!scm_is_tagged_array (x))
+    abort ();
+  return (struct scm_array *) SCM_UNPACK_POINTER (x);
+}
+
+static inline SCM
+scm_from_array (struct scm_array *x)
+{
+  return SCM_PACK_POINTER (x);
+}
+
+static inline size_t
+scm_array_dimension_count (struct scm_array *array)
+{
+  return array->tag_and_ndims >> 16;
+}
+
+static inline SCM
+scm_array_vector (struct scm_array *array)
+{
+  return array->vector;
+}
+
+static inline size_t
+scm_array_base (struct scm_array *array)
+{
+  return array->base;
+}
+
+SCM_INTERNAL struct scm_array* scm_i_make_array (SCM v, size_t base, int ndim);
+SCM_INTERNAL int scm_i_print_array (SCM array, SCM port, scm_print_state *pstate);
+
+SCM_INTERNAL void scm_init_arrays (void);
+
+#endif  /* SCM_ARRAYS_INTERNAL_H */