IBITS (integer, start-position, length)

  Class:  Elemental function - Generic

  Returns the value of the bits of the first argument specified by
  start-position and number of bits.  The low-order bit is position
  0.

  +------+---------+----------+------------+-------------+
  | Args | Generic | Specific |  Argument  | Result Type |
  +------+---------+----------+------------+-------------+
  |  3   |  IBITS  |   --     | INTEGER*1  | INTEGER*1   |
  |      |         | IIBITS   | INTEGER*2  | INTEGER*2   |
  |      |         | JIBITS   | INTEGER*4  | INTEGER*4   |
  |      |         | KIBITS   | INTEGER*8  | INTEGER*8   |
  +------+---------+----------+------------+-------------+