wpmu plugin-management mass activation

[yannux]

Mass activating wp-polls (2.50) on wpmu doesn't work because of

### Polls Table Name
global $wpdb;
$wpdb->pollsq = $wpdb->prefix.'pollsq';
$wpdb->pollsa = $wpdb->prefix.'pollsa';
$wpdb->pollsip	 = $wpdb->prefix.'pollsip';

is defined when the file is include once.

So I add between lines 1463,1464 :

$wpdb->pollsq = $wpdb->prefix.'pollsq';
$wpdb->pollsa = $wpdb->prefix.'pollsa';
$wpdb->pollsip	 = $wpdb->prefix.'pollsip';

making them defined with good $wpdb->prefix