Submits a numbered changelist to Perforce.
Note: P4Submit cannot (yet) submit the default changelist.
This shouldn't be a problem with the ANT task as the usual flow is
P4Change to create a new numbered change followed by P4Edit then P4Submit.
Example Usage:-
<p4submit change="${p4.change}" />
Called by the project to let the task do its work. This method may be
called more than once, if the task is invoked more than once.
For example,
if target1 and target2 both depend on target3, then running
"ant target1 target2" will run all tasks in target3 twice.