SPARK-5850: Remove experimental label for Scala 2.11 and FlumePollingStream

Author: Patrick Wendell <patrick@databricks.com>

Closes #4638 from pwendell/SPARK-5850 and squashes the following commits:

386126f [Patrick Wendell] SPARK-5850: Remove experimental label for Scala 2.11 and FlumePollingStream.

docs/building-spark.md

@@ -111,9 +111,9 @@ To produce a Spark package compiled with Scala 2.11, use the `-Dscala-2.11` prop
     dev/change-version-to-2.11.sh
     mvn -Pyarn -Phadoop-2.4 -Dscala-2.11 -DskipTests clean package
 
-Scala 2.11 support in Spark is experimental and does not support a few features.
-Specifically, Spark's external Kafka library and JDBC component are not yet
-supported in Scala 2.11 builds.
+Scala 2.11 support in Spark does not support a few features due to dependencies
+which are themselves not Scala 2.11 ready. Specifically, Spark's external 
+Kafka library and JDBC component are not yet supported in Scala 2.11 builds.
 
 # Spark Tests in Maven
 

docs/streaming-flume-integration.md

@@ -64,7 +64,7 @@ configuring Flume agents.
 
 3. **Deploying:** Package `spark-streaming-flume_{{site.SCALA_BINARY_VERSION}}` and its dependencies (except `spark-core_{{site.SCALA_BINARY_VERSION}}` and `spark-streaming_{{site.SCALA_BINARY_VERSION}}` which are provided by `spark-submit`) into the application JAR. Then use `spark-submit` to launch your application (see [Deploying section](streaming-programming-guide.html#deploying-applications) in the main programming guide).
 
-## Approach 2 (Experimental): Pull-based Approach using a Custom Sink
+## Approach 2: Pull-based Approach using a Custom Sink
 Instead of Flume pushing data directly to Spark Streaming, this approach runs a custom Flume sink that allows the following.
 
 - Flume pushes data into the sink, and the data stays buffered.

external/flume/src/main/scala/org/apache/spark/streaming/flume/FlumeUtils.scala

@@ -19,7 +19,6 @@ package org.apache.spark.streaming.flume
 
 import java.net.InetSocketAddress
 
-import org.apache.spark.annotation.Experimental
 import org.apache.spark.storage.StorageLevel
 import org.apache.spark.streaming.StreamingContext
 import org.apache.spark.streaming.api.java.{JavaReceiverInputDStream, JavaStreamingContext}
@@ -121,7 +120,6 @@ object FlumeUtils {
    * @param port Port of the host at which the Spark Sink is listening
    * @param storageLevel Storage level to use for storing the received objects
    */
-  @Experimental
   def createPollingStream(
       ssc: StreamingContext,
       hostname: String,
@@ -138,7 +136,6 @@ object FlumeUtils {
    * @param addresses List of InetSocketAddresses representing the hosts to connect to.
    * @param storageLevel Storage level to use for storing the received objects
    */
-  @Experimental
   def createPollingStream(
       ssc: StreamingContext,
       addresses: Seq[InetSocketAddress],
@@ -159,7 +156,6 @@ object FlumeUtils {
    *                    result in this stream using more threads
    * @param storageLevel Storage level to use for storing the received objects
    */
-  @Experimental
   def createPollingStream(
       ssc: StreamingContext,
       addresses: Seq[InetSocketAddress],
@@ -178,7 +174,6 @@ object FlumeUtils {
    * @param hostname Hostname of the host on which the Spark Sink is running
    * @param port     Port of the host at which the Spark Sink is listening
    */
-  @Experimental
   def createPollingStream(
       jssc: JavaStreamingContext,
       hostname: String,
@@ -195,7 +190,6 @@ object FlumeUtils {
    * @param port         Port of the host at which the Spark Sink is listening
    * @param storageLevel Storage level to use for storing the received objects
    */
-  @Experimental
   def createPollingStream(
       jssc: JavaStreamingContext,
       hostname: String,
@@ -212,7 +206,6 @@ object FlumeUtils {
    * @param addresses    List of InetSocketAddresses on which the Spark Sink is running.
    * @param storageLevel Storage level to use for storing the received objects
    */
-  @Experimental
   def createPollingStream(
       jssc: JavaStreamingContext,
       addresses: Array[InetSocketAddress],
@@ -233,7 +226,6 @@ object FlumeUtils {
    *                     result in this stream using more threads
    * @param storageLevel Storage level to use for storing the received objects
    */
-  @Experimental
   def createPollingStream(
       jssc: JavaStreamingContext,
       addresses: Array[InetSocketAddress],