Fix so "Open in new window" consistently displays "external window" interface (#6659)

Both 'show' and 'extwin' will use _extwin=1 argument.

CHANGELOG

@@ -6,6 +6,7 @@ CHANGELOG Roundcube Webmail
 - Elastic: Changed read/unread icons (#6636)
 - Elastic: Changed "Move to..." icon (#6637)
 - Elastic: Add hide/show for advanced preferences (#6632)
+- Fix so "Open in new window" consistently displays "external window" interface (#6659)
 - Fix bug where next row wasn't selected after deleting a collapsed thread (#6655)
 - Fix bug where external content (e.g. mail body) was passed to templates parsing code (#6640)
 

program/js/app.js

@@ -869,7 +869,7 @@ function rcube_webmail()
 
       case 'open':
         if (uid = this.get_single_uid()) {
-          obj.href = this.url('show', this.params_from_uid(uid));
+          obj.href = this.url('show', this.params_from_uid(uid, {_extwin: 1}));
           return true;
         }
         break;