Conform foreach tparam to majority naming convention

'U' is the common choice for the foreach function result tparam.

This command summarises the naming diversity before and after this change.

$ fgrep -r 'def foreach[' *|cut -f2 -d:|cut -f1 -d'('|tr -s ' '|sed 's/override //g'|sort|uniq -c|sort -nr

Before,

     80  def foreach[U]
      6  def foreach[C]
      6  def foreach[B]
      4  final def foreach[U]
      3  def foreach[S]
      2  inline final def foreach[U]
      2  def foreach[A]
      1  inline final def foreach[specialized
      1  final def foreach[B]
      1  * def foreach[U]
      1  def foreach[Q]
      1  def foreach[D]
      1  def foreach[A,B,U]

After,

     98  def foreach[U]
      5  final def foreach[U]
      2  inline final def foreach[U]
      1  inline final def foreach[specialized
      1  * def foreach[U]
      1  def foreach[A,B,U]

(@ symbols removed.)

1 files changed, 4 insertions, 4 deletions

diff --git a/src/library/scala/collection/immutable/Stream.scala b/src/library/scala/collection/immutable/Stream.scala
index a6c55f8828..d3be809255 100644
--- a/src/library/scala/collection/immutable/Stream.scala
+++ b/src/library/scala/collection/immutable/Stream.scala
@@ -176,9 +176,9 @@ import scala.language.implicitConversions
  *    loop(1, 1)
  *  }
  *  }}}
- * 
+ *
  *  Note that `mkString` forces evaluation of a `Stream`, but `addString` does
- *  not.  In both cases, a `Stream` that is or ends in a cycle 
+ *  not.  In both cases, a `Stream` that is or ends in a cycle
  *  (e.g. `lazy val s: Stream[Int] = 0 #:: s`) will convert additional trips
  *  through the cycle to `...`.  Additionally, `addString` will display an
  *  un-memoized tail as `?`.
@@ -566,7 +566,7 @@ self =>
       else super.flatMap(f)(bf)
     }
 
-    override def foreach[B](f: A => B) =
+    override def foreach[U](f: A => U) =
       for (x <- self)
         if (p(x)) f(x)
 
@@ -589,7 +589,7 @@ self =>
    *  unless the `f` throws an exception.
    */
   @tailrec
-  override final def foreach[B](f: A => B) {
+  override final def foreach[U](f: A => U) {
     if (!this.isEmpty) {
       f(head)
       tail.foreach(f)