[ticket/12704] Improve the load time information in the footer when enabled

PR #2570 has added new constant to display load time information without
debug mode is being on (https://tracker.phpbb.com/browse/PHPBB3-12687).
This patch expands the total load time info with SQL/PHP load times,
while hiding the additional info with <abbr> element.

<a href="https://tracker.phpbb.com/browse/PHPBB3-12704">PHPBB3-12704</a>.
I think that it make no sense to have this information translatable and not the other. And:
[2014-06-13 07:53:56] <Nicofuma> btw, these string should be translatable isn't it?
[2014-06-13 07:54:28] <nickvergessen> its debug information
[2014-06-13 07:54:33] <nickvergessen> can do that in the future
[2014-06-13 08:28:43] <bantu> i don't think this should be translatable
[2014-06-13 08:33:10] <bantu> let's not waste time on such crap

Otherwise, you should use $user->lang() istead of sprintf($user->lang[])