Change to Apache v2 Timsort

OpenJDK is GPLv2, not compatible. This Timsort is available under Apache v2
from the Android repo. Not to be confused with the identical code in OpenJDK7
which is under GPLv2. Go figure.

Author: aarondav

core/src/main/scala/org/apache/spark/util/collection/SortDataFormat.scala

@@ -43,7 +43,10 @@ private[spark] trait SortDataFormat[K, Buffer] extends Any {
   /** Copy a single element from src(srcPos) to dst(dstPos). */
   protected def copyElement(src: Buffer, srcPos: Int, dst: Buffer, dstPos: Int): Unit
 
-  /** Copy a range of elements starting at src(srcPos) to dst, starting at dstPos. */
+  /**
+   * Copy a range of elements starting at src(srcPos) to dst, starting at dstPos.
+   * Overlapping ranges are allowed.
+   */
   protected def copyRange(src: Buffer, srcPos: Int, dst: Buffer, dstPos: Int, length: Int): Unit
 
   /**