gnutls: bump to version 3.4.7

The 3.4 series has been promoted to stable.
Handle autodeps more concisely (idn, p11-kit, zlib).
libtasn1 is now mandatory, since otherwise gnutls uses the bundled
version it makes no sense to try that because of target duplication.
Disable tpm support since we've got no trousers package.
Disable libdane support since we've got no dane package.

Signed-off-by: Gustavo Zacarias <gustavo@zacarias.com.ar>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>