get avatar by nickname

This is to support third-party apps that want to build an URL to an
avatar given a user's name.

darcs-hash:20080711060045-84dde-08b0072de764d5b67ce7abe73fa0553f32de4ab3.gz

lib/util.php

@@ -780,6 +780,8 @@ function common_fancy_url($action, $args=NULL) {
 		return common_path('search/notice' . (($args) ? ('?' . http_build_query($args)) : ''));
 	 case 'noticesearchrss':
 		return common_path('search/notice/rss' . (($args) ? ('?' . http_build_query($args)) : ''));
+	 case 'avatarbynickname':
+		return common_path($args['nickname'].'/avatar/'.$args['size']);
 	 default:
 		return common_simple_url($action, $args);
 	}