Roundcube doesn't parse some IMAP charsets properly

[Gena01]

There's a bug that I experienced running against Dovecot in my setup.

[content-type] => text/plain; charset=ANSI_X3.4-1968

header got charset parsed as ANSI because of a bad regexp. It would parse it to ANSI and this is not a valid charset so I would get a missing Subject when viewing e-mails.

It took me a while to track this down, The fix is to edit the regexp in program/lib/imap.inc line 1302 to have updated regexp:

if (preg_match('/charset="?([a-z0-9\-\.\_]+)"?/i', $ctype_add, $regs))
  $result[$id]->charset = $regs[1];

I basically added support for . and _ in charset. With this patch I am getting the messages displayed properly now.