Don't build our differ if we don't have javaws.jar; fixed some deprecated

CopyUtils usage.

build.xml

@@ -34,6 +34,12 @@
     <condition property="build.torrent">
       <isset property="snark.present"/>
     </condition>
+    <available property="javaws.present"
+     classname="com.sun.javaws.jardiff.JarDiff" classpathref="clazzpath"/>
+    <echo message="Have Java Web Start: ${javaws.present}"/>
+    <condition property="build.differ">
+      <isset property="javaws.present"/>
+    </condition>
   </target>
 
   <!-- prepares the application directories -->
@@ -53,7 +59,7 @@
     <copy todir="${deploy.dir}/lib" flatten="true">
       <fileset refid="${app.name}.libs"/>
     </copy>
-    <copy todir="${deploy.dir}/lib" file="${java.home}/lib/javaws.jar"/>
+    <copy todir="${deploy.dir}/lib" file="${java.home}/lib/javaws.jar" failonerror="false"/>
   </target>
 
   <!-- cleans out the intermediate build files -->
@@ -74,6 +80,7 @@
            classpathref="clazzpath" includeAntRuntime="no"
            source="1.5" target="1.5">
       <exclude name="**/TorrentDownloader*" unless="build.torrent"/>
+      <exclude name="**/tools/Differ*" unless="build.differ"/>
       <compilerarg value="-Xlint:unchecked"/>
     </javac>
   </target>