Add NullOutputStream

This is in preparation for the Java 8 move, which doesn't support
nullOutputStream().

src/main/java/org/apache/harmony/unpack200/Archive.java

@@ -148,7 +148,7 @@ public class Archive {
                     segment.setLogLevel(logLevel);
                     segment
                             .setLogStream(logFile != null ? (OutputStream) logFile
-                                    : OutputStream.nullOutputStream());
+                                    : NullOutputStream.INSTANCE);
                     segment.setPreRead(false);
 
                     if (i == 1) {

src/main/java/org/apache/harmony/unpack200/NullOutputStream.java

@@ -0,0 +1,26 @@
+package org.apache.harmony.unpack200;
+
+import java.io.OutputStream;
+
+public final class NullOutputStream extends OutputStream {
+    public static final OutputStream INSTANCE = new NullOutputStream();
+
+    private NullOutputStream() {
+        /* empty */
+    }
+
+    @Override
+    public void write(int i) {
+        /* empty */
+    }
+
+    @Override
+    public void write(byte[] b) {
+        /* empty */
+    }
+
+    @Override
+    public void write(byte[] b, int off, int len) {
+        /* empty */
+    }
+}