Whether this instance of ProjectHelper can parse an Antlib descriptor given by the URL and return its content as an UnknownElement ready to be turned into an Antlib task.
This method should not try to parse the content of the descriptor, the URL is only given as an argument to allow subclasses to decide whether they can support a given URL scheme or not.
Subclasses that return true in this method must also override {@link #parseAntlibDescriptor parseAntlibDescriptor}.
This implementation returns false.
@since Ant 1.8.0