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. Anything said in
the manual page of typedef applies to taskdef as well.
<taskdef name="myjavadoc" classname="com.mydomain.JavadocTask"/>
makes a task called myjavadoc available to Apache Ant. The
class com.mydomain.JavadocTask implements the task.