http2 support

[drwetter]

see e.g https://http2.golang.org/

[drwetter]

Even with old Debian wheezy.openssl shows google.de is offering h2-15:

myprompt%: /testssl.sh -y google.de          

#########################################################
testssl.sh v2.3dev  (https://testssl.sh)
($Id: testssl.sh,v 1.201 2015/03/09 07:07:40 dirkw Exp $)

   This program is free software. Redistribution + 
   modification under GPLv2 is permitted. 
   USAGE w/o ANY WARRANTY. USE IT AT YOUR OWN RISK!

 Note: you can only check the server with what is
 available (ciphers/protocols) locally on your machine!
 #########################################################

 Using "OpenSSL 1.0.1e 11 Feb 2013" [~111 ciphers] on
 XXXXX:/usr/bin/openssl
 (built: "Jan  8 21:12:53 2015", platform: "debian-amd64")


Testing now (2015-03-16 10:49) ---> 74.125.136.94:443 (google.de) <---

 further IP addresses:   2a00:1450:4013:c01::5e
 rDNS (74.125.136.94):   ea-in-f94.1e100.net
 Service detected:       HTTP

 SPDY/NPN   h2-15, h2-14, spdy/3.1, spdy/3, http/1.1 (advertised)

Done now (2015-03-16 10:50) ---> 74.125.136.94:443 (google.de) <---

With OpenSSL 1.0.2 that doesn't change (ALPN support?):

myprompt% ./openssl64-1.0.2-static version                                        
OpenSSL 1.0.2 22 Jan 2015
myprompt% ./openssl64-1.0.2-static s_client -connect google.de:443 -nextprotoneg "" </dev/null       10:55:19
CONNECTED(00000003)
Protocols advertised by server: h2-15, h2-14, spdy/3.1, spdy/3, http/1.1
[..]