allocate a tc7 to arrays

allocate a tc7 to arrays

* libguile/tags.h (scm_tc7_array): Allocate a tag for arrays.
* libguile/arrays.h (SCM_I_ARRAYP): Change to use scm_tc7_array.  The
  previous definition was not externally usable because scm_i_tc16_array
  was internal.
  (scm_i_print_array): Declare, though internally.

* libguile/arrays.c (scm_i_make_array): Use scm_cell with the tc7
  instead of NEWSMOB.
  (scm_i_print_array): Make not static.
  (SCM_ARRAY_IMPLEMENTATION): Adapt.
  (scm_init_arrays): Remove array smob declaration.

* libguile/eq.c (scm_equal_p): Refactor to put the string, pointer, and
  bytevector cases in the switch.  Add a case for arrays.

* libguile/goops.c: Add <array> declarations.

* libguile/print.c (iprin1): Call scm_i_print_array as needed.

* libguile/evalext.c (scm_self_evaluating_p): Add a case for arrays.