Fix compilation problems wrt 3.0/databind

Author: cowtowncoder

src/main/java/com/fasterxml/jackson/dataformat/xml/ser/ToXmlGenerator.java

@@ -478,13 +478,6 @@ public void writeFieldId(long id) throws IOException {
         final String name = Long.toString(id);
         writeFieldName(name);
     }
-    
-    @Override
-    public final void writeStringField(String fieldName, String value) throws IOException
-    {
-        writeFieldName(fieldName);
-        writeString(value);
-    }
 
     // 03-Aug-2017, tatu: We could use this as mentioned in comment below BUT
     //    since there is no counterpart for deserialization this will not

src/main/java/com/fasterxml/jackson/dataformat/xml/util/XmlRootNameLookup.java

@@ -62,9 +62,8 @@ public QName findRootName(Class<?> rootType, MapperConfig<?> config)
     // for annotation introspection hence not needed any more
     protected QName _findRootName(Class<?> rootType, MapperConfig<?> config)
     {
-        BeanDescription beanDesc = config.introspectClassAnnotations(rootType);
-        AnnotationIntrospector intr = config.getAnnotationIntrospector();
-        AnnotatedClass ac = beanDesc.getClassInfo();
+        final AnnotatedClass ac = config.introspectClassAnnotations(rootType);
+        final AnnotationIntrospector intr = config.getAnnotationIntrospector();
         String localName = null;
         String ns = null;