[arch-general] new build of mutt in [testing]

Hi everyone, I have made a new build of mutt with two significant changes: 1. Use ncurses rather than slang. (Slang made sense before, but ncurses supports Unicode now, is more featureful and popular, and MuttWiki recommends it as a solution to many slang-related problems.) 2. Use libidn for internationalized domain name support. As emails are important, the build is now in [testing] and I will wait a few days before moving it to [extra]. Feedback is welcome! Cheers. -- Gaetan