Fix DList.insertFront(range) regression - #15263.

As createNode was taking a value by ref, Dlist.insertFront could not be
called with a range with a non-ref front.

Fix by taking the value as `auto ref` instead of just `ref`.
Resolves #15263.

std/container/dlist.d

@@ -163,7 +163,7 @@ struct DList(T)
   private
   {
     //Construct as new PayNode, and returns it as a BaseNode.
-    static BaseNode* createNode(Stuff)(ref Stuff arg, BaseNode* prev = null, BaseNode* next = null)
+    static BaseNode* createNode(Stuff)(auto ref Stuff arg, BaseNode* prev = null, BaseNode* next = null)
     {
         return (new PayNode(BaseNode(prev, next), arg)).asBaseNode();
     }
@@ -936,3 +936,11 @@ private:
 
     DList!ITest().insertBack(new Test());
 }
+
+@safe unittest //15263
+{
+    import std.range : iota;
+    auto a = DList!int();
+    a.insertFront(iota(0, 5)); // can insert range with non-ref front
+    assert(a.front == 0 && a.back == 4);
+}