Fixes SI-5328. Iterator.patched failed when from=0.

It turns out iterator.patched forgot to drop replacement values if they were at the beginning.
This is because the index was advancing before checking to see if replaced elements should be
dropped.   Moved this behavior to the beginning of next.

src/library/scala/collection/Iterator.scala

@@ -1079,11 +1079,12 @@ trait Iterator[+A] extends TraversableOnce[A] {
       if (i < from) origElems.hasNext
       else patchElems.hasNext || origElems.hasNext
     def next(): B = {
+      // We have to do this *first* just in case from = 0.
+      if (i == from) origElems = origElems drop replaced
       val result: B =
         if (i < from || !patchElems.hasNext) origElems.next()
         else patchElems.next()
       i += 1
-      if (i == from) origElems = origElems drop replaced
       result
     }
   }

test/files/run/t5328.check

@@ -0,0 +1,3 @@
+2
+1,2,8
+1,8,3

test/files/run/t5328.scala

@@ -0,0 +1,5 @@
+object Test extends App {
+  println(Vector(1).view.updated(0,2).toList mkString ",")
+  println(Seq(1,2,3).view.updated(2,8).toList mkString ",")
+  println(List(1,2,3).view.updated(1,8).toList mkString ",")
+}