[ticket/11463] Add title attribute to topics in search results

We use this title attribute in viewforum_body.html, but not in
search_results.html. Perhaps we should, as this will maintain
consitency between all these topic view pages.

PHPBB3-11463
Merge pull request #1312 from VSEphpbb/ticket/11463

[ticket/11463] Add title attribute to topics in search results