all_distinct/1: free "visited" attribute for users
all_distinct/1: free "visited" attribute for users

Before:

   %?- put_attr(Y, visited, true), A=[X, B, 4, Y], A ins 1..4, B#\=2, B#\=1, all_distinct(A), X = 2.
   %@ false.

Now:

   %?- put_attr(Y, visited, true), A=[X, B, 4, Y], A ins 1..4, B#\=2, B#\=1, all_distinct(A), X = 2.
   %@ Y = 1,
   %@ A = [2, 3, 4, 1],
   %@ X = 2,
   %@ B = 3.

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