new package: libtasn1

Libtasn1 is the ASN.1 library used by GnuTLS, GNU Shishi and some
other packages. It was written by Fabio Fiorina, and has been
shipped as part of GnuTLS for some time but is now a proper
GNU package.

[Peter: Both licenses are '+']
Signed-off-by: Stefan Fröberg <stefan.froberg@petroprogram.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>