Reverted addition of 5 specialized method from LinearSeqOptimized to …

…List.

It seems any gains were more then compensated by the loss of making map polymorphic, probably preventing inlining decisions in Hotspot.

src/library/scala/collection/immutable/List.scala

@@ -310,62 +310,6 @@ sealed abstract class List[+A] extends AbstractSeq[A]
       these = these.tail
     }
   }
-
-  @inline override /*TraversableLike*/
-  def map[B, That](f: A => B)(implicit bf: CanBuildFrom[List[A], B, That]): That = {
-    val b = bf(repr)
-    var these = this
-    while (!these.isEmpty) {
-      b += f(these.head)
-      these = these.tail
-    }
-    b.result
-  }
-
-  @inline override /*TraversableLike*/
-  def flatMap[B, That](f: A => GenTraversableOnce[B])(implicit bf: CanBuildFrom[List[A], B, That]): That = {
-    val b = bf(repr)
-    var these = this
-    while (!these.isEmpty) {
-      b ++= f(these.head).seq
-      these = these.tail
-    }
-    b.result
-  }
-
-  @inline override /*TraversableLike*/
-  def filter(p: A => Boolean): List[A] = {
-    val b = newBuilder
-    var these = this
-    while (!these.isEmpty) {
-      val x = these.head
-      if (p(x)) b += x
-      these = these.tail
-    }
-    b.result
-  }  
-
-  @inline override /*TraversableLike*/
-  def filterNot(p: A => Boolean): List[A] = {
-    val b = newBuilder
-    var these = this
-    while (!these.isEmpty) {
-      val x = these.head
-      if (!p(x)) b += x
-      these = these.tail
-    }
-    b.result
-  }  
-
-  @inline override /*SeqLike*/
-  def contains(elem: Any): Boolean = {
-    var these = this
-    while (!these.isEmpty) {
-      if (these.head == elem) return true
-      these = these.tail
-    }
-    false
-  }
 
   @deprecated("use `distinct` instead", "2.8.0")
   def removeDuplicates: List[A] = distinct