i386.md (maxmin): New code iterator.

i386.md (maxmin): New code iterator.

	* config/i386/i386.md (maxmin): New code iterator.
	* config/i386/sse.md (<maxmin:code><mode>3): Macroize expander
	from <umaxmin:code><mode>3 and <smaxmin:code><mode>3 using maxmin
	code iterator.
	(*avx2_<maxmin:code><mode>3): Macroize isn from
	*avx2_<umaxmin:code><mode>3 and *avx2_<smaxmin:code><mode>3 using
	maxmin code iterator.
	(<smaxmin:code><VI124_128:mode>3): Merge with <smaxmin:code>v8hi3.
	(<umaxmin:code><VI124_128:mode>3): Merge with umaxv4si3 and
	<umaxmin:code>v16qi3.

From-SVN: r178981