SR: version update and spec file cleanup

- update to 3.0
* t-prot: Umlauts always are so wrong. Hopefully Outlook mails in
German are handled fine now.
* t-prot.1: Make clear that --pgp-move and --pgp-move-vrf also work
on SSL output.
* t-prot: Coding style cleanup in pgp().
* t-prot: Fix detection of unified diffs in the message body when
using --diff.
* t-prot.1: Update year.
* contrib/t-prot.sl: Reflect transition to slang2 in comments.
* contrib/t-prot.sl: Drop support for slang-1, default to slang-2.
* t-prot, contrib/muttrc.t-prot: Drop support for mutt-1.4. Default
to mutt-1.5.x strings.
* t-prot: Fix eYou Webmail Tofu.
* t-prot: Fix text/plain content-type detection with several user
agents. (forwarded request 213927 from dsterba)