More sync in close() methods

Conflicts:
	source/net/yacy/kelondro/logging/GuiHandler.java
	source/net/yacy/kelondro/workflow/InstantBusyThread.java

source/net/yacy/kelondro/logging/GuiHandler.java

@@ -208,8 +208,8 @@ public class GuiHandler extends Handler {
         
     }
 
-    public void close() throws SecurityException {
-        
+    public synchronized void close() throws SecurityException {
+        // Nothing implement here
     }
 
 }

source/net/yacy/kelondro/workflow/InstantBusyThread.java

@@ -182,4 +182,14 @@ public final class InstantBusyThread extends AbstractBusyThread implements BusyT
         return oneTimeJob( thread, startupDelay);
     }
 
+    @Override
+    public void open() {
+        // Not implemented in this thread
+    }
+
+    @Override
+    public synchronized void close() {
+     // Not implemented in this thread
+    }
+
 }

source/net/yacy/search/index/DocumentMetadata.java

@@ -50,7 +50,7 @@ public class DocumentMetadata implements Metadata {
 	}
 
 	@Override
-	public void close() {
+	public synchronized void close() {
 		// TODO Auto-generated method stub
 		
 	}

source/net/yacy/search/index/DocumentReference.java

@@ -42,7 +42,7 @@ public class DocumentReference {
     	return data.size();
     }
 
-    public void close() {
+    public synchronized void close() {
     	if (data != null) {
     		data.close();
     	}