stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator): Set up a default value of bitregion_end_.

gcc/
	* stor-layout.c (bit_field_mode_iterator::bit_field_mode_iterator):
	Set up a default value of bitregion_end_.
	(bit_field_mode_iterator::next_mode): Always apply bitregion_end_
	check.  Include SLOW_UNALIGNED_ACCESS in the alignment check.
	(get_best_mode): Ignore modes that are wider than the alignment.

From-SVN: r193604