allo 303 and 304 http status to be validated

The linkchecker flows MOVED_TEMPORARILY moved links but sikps MOVED_PERMANENTLY while there are as valid as MOVED_TEMPORARILY

example:
http://www.mmbase.org/license

resolution:
add
import org.apache.commons.httpclient.HttpStatus;
to the class imports

in HTTPLinkValidator at row 108 change the code to
if (gm.getStatusCode() == HttpStatus.SC_MOVED_TEMPORARILY || gm.getStatusCode() == HttpStatus.SC_MOVED_PERMANENTLY)

(and a small cleanup )
row 121
if (gm.getStatusCode() == HttpStatus.SC_OK)