Added a new forum feature: OS and Browser info.

Every post made in this forum will now store the OS and the browser used to make that specific post.
Info is visible in postbits area, the area of each post that show user info

<<<----------------| (PostBits area)

This option is active only starting from now so posts made before now will not have this info: there's no way to go back in history to get the OS and Browser for old posts.