Add template event "index_body_forumlist_before"

http://area51.phpbb.com/phpBB/viewtopic.php?f=111&t=44027&p=251891

Identifier: index_body_forumlist_before

Prosilver: In index_body.html around line 15, above <!-- INCLUDE forumlist_body.html -->

Subsilver: In index_body.html around line 11, above <!-- INCLUDE forumlist_body.html -->

Explanation: So extensions can add content to the top of the index page (after the page header links list, but before the start of the forums list).

Possible uses include advertisement MODs, Announcement or Welcome Center MODs... Any MOD that needs to inject something above the forums list (only on the forum index page).