remove needless dead.letter function (at least on embedded devices)
backport debian fixes (slightly modified)

compile tested. Please apply to upstream - thank you!

Signed-off-by: Dirk Brenken <dirk@brenken.org>

Drop gnutls and use openssl instead, due to excessive memory consumption in embedded environment for an additonal ssl library.

Signed-off-by: Dirk Brenken <dibdot@gmail.com>

Signed-off-by: Dirk Brenken <dibdot@gmail.com>