Mid engine setup [SU]ABDL

Mid engine setup [SU]ABDL

This updates vect_recog_abd_pattern to recognize the widening
variant of absolute difference (ABDL, ABDL2).

gcc/ChangeLog:

	* internal-fn.def (VEC_WIDEN_ABD): New internal hilo optab.
	* optabs.def (vec_widen_sabd_optab,
	vec_widen_sabd_hi_optab, vec_widen_sabd_lo_optab,
	vec_widen_sabd_odd_even, vec_widen_sabd_even_optab,
	vec_widen_uabd_optab,
	vec_widen_uabd_hi_optab, vec_widen_uabd_lo_optab,
	vec_widen_uabd_odd_even, vec_widen_uabd_even_optab):
	New optabs.
	* doc/md.texi: Document them.
	* tree-vect-patterns.cc (vect_recog_abd_pattern): Update to
	to build a VEC_WIDEN_ABD call if the input precision is smaller
	than the precision of the output.
	(vect_recog_widen_abd_pattern): Should an ABD expression be
	found preceeding an extension, replace the two with a
	VEC_WIDEN_ABD.