[ticket/12506] Reposition post-buttons for compact layout

Fixes "Long post titles bump the username down an extra row beneath the edit/quote/delete buttons"

I added the `.has-profile` class to `post` because we use `.post` a lot, in very different contexts. Some are full (viewtopic), and some are very small/compact (post review/mcp/etc). This class will help us distinguish between "full" posts and "compact" ones.

![postbuttons-abspos](https://cloud.githubusercontent.com/assets/3015760/3614616/cd7d213e-0dc1-11e4-8f31-0b6549f070f6.png)

https://tracker.phpbb.com/browse/PHPBB3-12506
PHPBB3-12506