Update translator documentation.

i18n/L10n updates.
Whitespace update.

plugins/SubMirror/lib/addmirrorform.php

@@ -57,11 +57,13 @@ class AddMirrorForm extends Form
         $this->li();
         $this->doInput('addmirror-feedurl',
                        'feedurl',
+                       // TRANS: Field label.
                        _m('Web page or feed URL:'),
                        $this->out->trimmed('feedurl'));
         $this->unli();
 
         $this->li();
+        // TRANS: Button text for adding a feed.
         $this->out->submit('addmirror-save', _m('BUTTON','Add feed'));
         $this->unli();
         $this->out->elementEnd('ul');