Add until(cond; next); fix #639

tests/all.test

@@ -250,6 +250,10 @@ null
 1
 [1,2,4,8]
 
+[.[]|[.,1]|until(.[0] < 1; [.[0] - 1, .[1] * .[0]])|.[1]]
+[1,2,3,4,5]
+[1,2,6,24,120]
+
 [foreach .[] as $item ([3, null]; if .[0] < 1 then break else [.[0] -1, $item] end; .[1])]
 [11,22,33,44,55,66,77,88,99]
 [11,22,33]