Allow Content-Disposition variables like 'filename*0*'

At least one version of Thunderbird produces attachments with a header
like this:

-- snip --
Content-Disposition: attachment;
 filename*0*=ISO-8859-15''%32%30%31%31%20%4E%6F%76%20%32%35%20%66%FC%72%20;
 filename*1*=%4A%6F%68%61%6E%6E%65%73%20%32%2E%6F%64%74
-- snap --

Let's cope with those, too.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Allow Content-Disposition settings like filename*=''...

At least one version of Microsoft Entourage produces Content-Disposition
headers like this one:

-- snip --
Content-disposition: attachment;
 filename*=''Study%20Informati%8Ar%20Singers_B.doc
-- snap --

Let's cope with them, too.

Unfortunately, it seems that there is no way to convince the DFA to handle

-- snip --
Content-Disposition: attachment;
 filename*=Imaris%207.4%20-%20Release%20Notes%20-%20draft.pdf
-- snap --

too (produced by ColdFusion 8 Application Server). The problem is that we
cannot have a rule with two branches one of which wants to copy to 'value'
and one of which wants to copy to 'minor'.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Fix whitespace

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Remove unused variables (fix compiler warnings)