[SPARK-1232] Fix the hadoop 0.23 yarn build

Author: Thomas Graves <tgraves@apache.org>

Closes #127 from tgravescs/SPARK-1232 and squashes the following commits:

c05cfd4 [Thomas Graves] Fix the hadoop 0.23 yarn build

core/pom.xml

@@ -30,6 +30,18 @@
   <packaging>jar</packaging>
   <name>Spark Project Core</name>
   <url>http://spark.apache.org/</url>
+  <!-- SPARK-1121: Adds an explicit dependency on Avro to work around a Hadoop 0.23.X issue -->
+  <profiles>
+    <profile>
+      <id>yarn-alpha</id>
+      <dependencies>
+        <dependency>
+          <groupId>org.apache.avro</groupId>
+          <artifactId>avro</artifactId>
+        </dependency>
+      </dependencies>
+    </profile>
+  </profiles>
 
   <dependencies>
     <dependency>