Update plexus-util and plexus interpolation to match transitive deps from Maven 2.2.1.

git-svn-id: https://svn.apache.org/repos/asf/maven/ant-tasks/trunk@885836 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/pom.xml b/pom.xml
index d9e3560..a48c13f 100644
--- a/pom.xml
+++ b/pom.xml
@@ -86,12 +86,12 @@
     <dependency>
       <groupId>org.codehaus.plexus</groupId>
       <artifactId>plexus-utils</artifactId>
-      <version>1.5.5</version>
+      <version>1.5.15</version>
     </dependency>
     <dependency>
       <groupId>org.codehaus.plexus</groupId>
       <artifactId>plexus-interpolation</artifactId>
-      <version>1.9</version>
+      <version>1.11</version>
     </dependency>
     <dependency>
       <groupId>org.apache.maven</groupId>