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, 1 insertions, 1 deletions

diff --git a/src/library/scala/collection/generic/TraversableForwarder.scala b/src/library/scala/collection/generic/TraversableForwarder.scala
index 1d7974f7a4..359ea402b6 100644
--- a/src/library/scala/collection/generic/TraversableForwarder.scala
+++ b/src/library/scala/collection/generic/TraversableForwarder.scala
@@ -32,7 +32,7 @@ trait TraversableForwarder[+A] extends Traversable[A] {
   /** The traversable object to which calls are forwarded. */
   protected def underlying: Traversable[A]
 
-  override def foreach[B](f: A => B): Unit = underlying foreach f
+  override def foreach[U](f: A => U): Unit = underlying foreach f
   override def isEmpty: Boolean = underlying.isEmpty
   override def nonEmpty: Boolean = underlying.nonEmpty
   override def size: Int = underlying.size