Fix binary compatibility.

Author: viirya

mllib/src/main/scala/org/apache/spark/mllib/linalg/Matrices.scala

@@ -78,12 +78,19 @@ sealed trait Matrix extends Serializable {
   }
 
   /** Convenience method for `Matrix`-`DenseVector` multiplication. */
+  def multiply(y: DenseVector): DenseVector = {
+    val output = new DenseVector(new Array[Double](numRows))
+    BLAS.gemv(1.0, this, y, 0.0, output)
+    output
+  }
+ 
+  /** Convenience method for `Matrix`-`Vector` multiplication. */
   def multiply(y: Vector): DenseVector = {
     val output = new DenseVector(new Array[Double](numRows))
     BLAS.gemv(1.0, this, y, 0.0, output)
     output
   }
-
+ 
   /** A human readable representation of the matrix */
   override def toString: String = toBreeze.toString()