java.net.URL.setURLStreamHandlerFactory() doesn't clear handlers cache

This could be bad for HotJava under JavaOS, if we ever decide to use
setURLStreamHandlerFactory (and we might). JavaOS uses the http protocol
before HotJava gets to run, so the http handler would already have been
recorded in java.net.URL.handlers.

The fix is trivial. Add this line to java.net.URL:

    public static synchronized void setURLStreamHandlerFactory(URLStreamHandlerF
actory fac) {
        if (factory != null) {
            throw new Error("factory already defined");
        }
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
            security.checkSetFactory();
        }
--> handlers = new Hashtable()
        factory = fac;
    }

A Pumpkin fix would be desirable