[MJAVADOC-705] Upgrade Maven Reporting API to 3.1.0

Move to new API signature, but maintain old binary compatibility. This, in
general, can be avoided by extending AbstractMavenReport.

This closes #120

pom.xml

@@ -207,7 +207,7 @@ under the License.
     <dependency>
       <groupId>org.apache.maven.reporting</groupId>
       <artifactId>maven-reporting-api</artifactId>
-      <version>3.0</version>
+      <version>3.1.0</version>
     </dependency>
     <dependency>
       <groupId>org.apache.maven</groupId>

src/main/java/org/apache/maven/plugins/javadoc/JavadocReport.java

@@ -27,6 +27,7 @@
 import java.util.ResourceBundle;
 import java.util.stream.Collectors;
 
+import org.apache.maven.doxia.sink.Sink;
 import org.apache.maven.doxia.siterenderer.RenderingContext;
 import org.apache.maven.doxia.siterenderer.sink.SiteRendererSink;
 import org.apache.maven.plugin.MojoExecutionException;
@@ -38,7 +39,6 @@
 import org.apache.maven.plugins.annotations.ResolutionScope;
 import org.apache.maven.reporting.MavenReport;
 import org.apache.maven.reporting.MavenReportException;
-import org.codehaus.doxia.sink.Sink;
 import org.codehaus.plexus.util.StringUtils;
 
 /**
@@ -123,6 +123,12 @@ public String getDescription( Locale locale )
         return description;
     }
 
+    public void generate( org.codehaus.doxia.sink.Sink sink, Locale locale )
+        throws MavenReportException
+    {
+        generate( (Sink) sink, locale );
+    }
+
     /** {@inheritDoc} */
     @Override
     public void generate( Sink sink, Locale locale )