* corelow.c (add_to_thread_list): Make sure reg_sect is non-null

	* corelow.c (add_to_thread_list):  Make sure reg_sect is non-null
	before de-referencing it.  Prevents deref of NULL pointer if core
	file lacks .reg section.
	* defs.h:  Rename floatformat_{to from}_long_double to
	floatformat_{to from}_doublest.  Get rid of FLOATFORMAT_{TO
	FROM}... macros.
	* findvar.c (extract_floating store_floating):  Change all refs to
	FLOATFORMAT_{FROM TO}... to floatformat_{from to}_doublest.
	* utils.c:  Change floatformat_{to from}_long_double to
	floatformat_{to from}_doublest cuz the new routines will use
	whatever size (double or long double) is appropriate.
	* config/i960/tm-i960.h (REGISTER_CONVERT_TO_VIRTUAL
	REGISTER_CONVERT_TO_RAW):  Change FLOATFORMAT... macros to
	floatformat... routine calls.