extract_bit_field_c

	status.i4.v = extract_bit_field_c(value.g.v, value_length.i4.v,
					  start_bit.i4.v, num_bits.i4.v,
					  field_value.g.v)

	This routine extracts the requested bit field from a value.  The
	original value must be no more than 8 bytes in length.

	value		memory location containing bit field
	value_length	value length in bytes (1, 2, 4, or 8)
	start_bit	low order bit number of field (starts at 0)
	num_bits	number of bits in field
	field_value	returned field value

	This function returns ACNET status values as follows:

	OK			success
	CLIB_INVARG		invalid starting bit number, number of bits,
				or value length

	This function requires the following include files:

	clib_h, acnet_errors_h

	Related functions:

	set_bit_field_c, bit_count_c, masked_off_bit_count_c,
	bit_field_circular_shift_c, icshft, setbit(_c), rstbit(_c),
	tstbit(_c)

	C/C++ usage:

	int	status;
	int	value = VALUE;
	int	value_length = 4;
	int	start_bit = 8;
	int	num_bits = 4;
	int	field_value;

	status = extract_bit_field_c((void *) &value,value_length,start_bit,
				     num_bits,(void *) &field_value);