dtls: dissect tls extensions

This adds dissection for more TLS extensions. The code was mostly
copied from the SSL dissector.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
dtls: set ssl_set_server()

To decrypt packages wireshark has to know if this is a client or a
server package. Setting this member was missing in the DTLS code.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
ssl: use hex numbers of TLS Cipher suites

The TLS Cipher Suites are referenced in Hex code everywhere, use that
also in the decode table.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
SSL: add decrypt support for CCM and CCM_8 Ciphers

This adds decrypt support for CCM and CCM_8 Ciphers like the ones
specified in rfc6655.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
dtls: add psk decrypt support

This adds support for decryption of DTLS packages when a PSK cipher was
used.

The code for generating a pre master secret was moved from packet-ssl.c
into packet-ssl-utils.c and packet-dtls.c now uses the same code to
generate a pre master secret.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>