Some improvements in RSS:

- Article's author is showed if present.
- In forum posts feeds, show post->subject instead of discussion->name
- Description contents in every article are passed to format_text() to
  show contents like the rest of Moodle.

lang/en/moodle.php

@@ -108,6 +108,7 @@ $string['blocks'] = 'Blocks';
 $string['blocksetup'] = 'Setting up block tables';
 $string['blocksuccess'] = '$a tables have been set up correctly';
 $string['bycourseorder'] = 'By course order';
+$string['byname'] = 'by $a';
 $string['cancel'] = 'Cancel';
 $string['categories'] = 'Course categories';
 $string['category'] = 'Category';