[ticket/13105] Add a test for relative dates

PHPBB3-13105
[ticket/13105] Do not display future dates 2+ days ahead as "tomorrow"

PHPBB3-13105
Merge pull request #2995 from nickvergessen/ticket/13105

[ticket/13105] Future relative dates are always displayed as "Tomorrow"

* nickvergessen/ticket/13105:
  [ticket/13105] Do not display future dates 2+ days ahead as "tomorrow"
  [ticket/13105] Add a test for relative dates