Added javadoc generation

modules/java/build.xml.in

@@ -2,6 +2,7 @@
 <!-- process, this config is used to package the autogenerated .java -->
 <!-- interface files into OpenCV.jar -->
 <project name="OpenCV">
+
   <target name="jar">
     <!-- This is to make a jar with a source attachment, for e.g. easy -->
     <!-- navigation in Eclipse. See this question: -->
@@ -10,7 +11,21 @@
       <include name="**/*.java"/>
       <compilerarg line="-encoding utf-8"/>
     </javac>
-
     <jar basedir="src" destfile="bin/@JAR_NAME@"/>
   </target>
+
+  <target name="javadoc">
+    <tstamp>
+      <format property="doctimestamp" pattern="EEE MMM d yyyy HH:mm:ss z"/>
+    </tstamp>
+    <javadoc
+      packagenames="org.opencv.*"
+      sourcepath="src"
+      destdir="doc/javadoc"
+      Windowtitle="OpenCV @OPENCV_VERSION_PLAIN@ Java documentation"
+      Doctitle="OpenCV Java documentation (@OPENCV_VERSION@)"
+      bottom="Generated on ${doctimestamp} / OpenCV @OPENCV_VCSVERSION@"
+      />
+  </target>
+
 </project>