This new framework should ease development of tasks that need to
execute external processes.

<exec> now invokes ExecTask, a reimplementation of Exec that uses the
new framework but has some additional features.

Submitted by:	Thomas Hass <thomas.haas@softwired-inc.com>


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@267799 13f79535-47bb-0310-9956-ffa450edef68