Reworked the patch by Eric Barboni.

The patch by Eric Barboni gathers maven archives from archive.apache.org
in both old and new directory layout. This patch, as suggested by David
J. M. Karlsen gathers archives only from maven central.

ant_maven.groovy

@@ -65,7 +65,7 @@ def altListUp(url,pattern) {
         if(m.find() ) {
             l=a.hrefAttribute.length()-2;
             ver=a.hrefAttribute.getAt(0..l);
-            url = p.getFullyQualifiedUrl(a.hrefAttribute+"binaries/");
+            url = p.getFullyQualifiedUrl(a.hrefAttribute);
             HtmlPage pb = wc.getPage(url);
             return pb.getAnchors().collect { HtmlAnchor a1 ->
               n = pattern.matcher(a1.hrefAttribute)
@@ -86,6 +86,4 @@ def store(key,o) {
 }
 
 store("hudson.tasks.Ant.AntInstaller",  listUp("http://archive.apache.org/dist/ant/binaries/",  "ant-([0-9.]+)-bin.zip\$").sort ( sortingversion  ))
-store("hudson.tasks.Maven.MavenInstaller", listUp("http://archive.apache.org/dist/maven/binaries/","maven-([0-9.]+)(-bin)?.zip\$").plus(altListUp("http://archive.apache.org/dist/maven/maven-3/","maven-([0-9.]+)(-bin)?.zip\$")).unique(false) {
-        a ,b -> a.id <=> b.id
-}.sort(sortingversion))
+store("hudson.tasks.Maven.MavenInstaller", altListUp("http://repo1.maven.org/maven2/org/apache/maven/apache-maven/","maven-([0-9.]+)(-bin)?.zip\$").sort(sortingversion))