 ra .  indices
     Return the array slice RA[INDICES ..., ...] The rank of RA must
     equal to the number of indices or larger.

     See also `array-ref', `array-cell-ref', `array-cell-set!'.

     `array-slice' may return a rank-0 array.  For example:

          (array-slice #2((1 2 3) (4 5 6)) 1 1) ==> #0(5)
          (array-slice #2((1 2 3) (4 5 6)) 1) ==> #(4 5 6)
          (array-slice #2((1 2 3) (4 5 6))) ==> #2((1 2 3) (4 5 6))
          (array-slice #0(5) ==> #0(5).

