When running wq_maker, the workspace of the worker was not cleaned up if the
worker process was sent a SIGINT. The reason - each task at the worker creates a
bunch of symlinks to files. When the worker tries to clean up its workspace, the
files are deleted before their symlinks leading to dangling symlinks. This
commit fixes this bug.
Remove extension in wq_maker.pl.
Add the cctools copyright boilerplate to wq_maker.