wakaba+dx

This is wakaba 3.0.9 with the following features backported from
wakaba+desuchan:

- User and admin post editing
- Inline post deletion
- DUPE_CHECK config entry
- noko (seriously, wakaba?)

No multiple board support, no staff account system, no fancy admin interface.
Should be a drop-in replacement, no db changes required. Changed files:

- wakaba.pl
- strings_en.pl
- futaba_style.pl
- wakaba3.js

Editing posts does *not* mark them as edited in a way that is visible to
everyone else (and no timestamp / ip is saved), as this would require database
modifications.

DUPE_CHECK: I tried to avoid changing the config files, so add this line to your
config.pl to disable duplicate file checking:

    use constant DUPE_CHECK => 0;

All the credit for these wakaba modifications goes to K_Anonymous (k-anon on
github), I just backported them because someone needed just a wakaba with post
editing.