trigger_twice/1 -> trigger_once/1
trigger_twice/1 -> trigger_once/1

With the current solver, I could not reconstruct a case where
triggering a constraint only once after posting yields
counter-intuitive results, and triggering it twice improves it. In any
case, this should happen automatically, not manually.

edechter/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,koryonik/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,mndrix/swipl-devel,koryonik/swipl-devel,jn7163/swipl-devel,edechter/swipl-devel,edechter/swipl-devel,mndrix/swipl-devel,jn7163/swipl-devel,koryonik/swipl-devel,koryonik/swipl-devel