[feature/revisions] Disable radio buttons if there's only one  revision left.

PHPBB3-10755
[feature/revisions] Move "Current Post" under revisions column.

- Adjust column widths.
- Adjust visibility of out-of-range rows.

PHPBB3-10755
[feature/revisions] Rename U_PROFILE as it conflicts with global var.

PHPBB3-10755