i386: Do not align small stack slots to 16 bytes

i386: Do not align small stack slots to 16 bytes

As Shmuel reported in <https://gcc.gnu.org/ml/gcc-help/2017-03/msg00009.html>,
on x86-64 small structures in automatic storage are aligned to 16 bytes.
This seems to be because of a mix-up between bits and bytes in the i386
target code.

	* config/i386/i386.c (ix86_local_alignment): Align most aggregates
	of 16 bytes and more to 16 bytes, not those of 16 bits and more.

From-SVN: r245949