* doublest.c (convert_floatformat_to_doublest): Use fmt->split_half

	* doublest.c (convert_floatformat_to_doublest): Use fmt->split_half
	for IBM long double nan and inf.
	(floatformat_is_negative, floatformat_classify,
	floatformat_mantissa): Similarly.
	(floatformat_ieee_single, floatformat_ieee_double,
	floatformat_ieee_quad, floatformat_arm_ext,
	floatformat_ia64_spill): Delete unused vars.
	(_initialize_doublest): Delete unused function.
	* gdbtypes.c (floatformats_ibm_long_double): Use new big- and
	little-endian variants of floatformat_ibm_long_double.