hoon: add +lure, for turning a singleton into a list
|* [a=(list) b=*]
(weld a ^+(a [b]~))
::
+:: +lure: List pURE
+++ lure
+ |* a=*
+ [i=a t=~]
+::
++ fand :: all indices
~/ %fand
|= [nedl=(list) hstk=(list)]
