Adds a task definition to the current project, such that this new task can be used in the current project.
This task is a form of Typedef with the attributes "adapter" and "adaptto" set to the values "org.apache.tools.ant.TaskAdapter" and "org.apache.tools.ant.Task" respectively.
<taskdef name="myjavadoc" classname="com.mydomain.JavadocTask"/>
makes a task called myjavadoc
available to Ant. The class com.mydomain.JavadocTask
implements the task.