Made sure that every call to bfd_read, bfd_write, and bfd_seek

	Made sure that every call to bfd_read, bfd_write, and bfd_seek
	checks the return value and handled bfd_error correctly.  These
	changes are not itemised.  Also:
	* oasys.c (oasys_read_record): Change return type to boolean.
	(oasys_slurp_symbol_table: Check oasys_read_record return value.
	(oasys_object_p, oasys_slurp_section_data): Likewise.
	(oasys_write_record): Change return type to boolean.
	(oasys_write_syms): Likewise.  Also, check oasys_write_record
	return value.
	(oasys_write_sections): Check oasys_write_record return value.
	(oasys_write_header): Change return type to boolean.  Check
	oasys_write_record return value.
	(oasys_write_end, oasys_write_data): Likewise.
	(oasys_write_object_contents): Check return values of
	oasys_write_header, oasys_write_syms, oasys_write_data, and
	oasys_write_end.