Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>

Avoid occasional up to 8% performance drops.

When verifying a partial path always check to see if the EE certificate
is explicitly trusted: the path could contain other untrusted certificates.

Experimental support for encrypt then mac from
draft-gutmann-tls-encrypt-then-mac-02.txt

To enable it set the appropriate extension number (0x10 for the test server)
using e.g. -DTLSEXT_TYPE_encrypt_then_mac=0x10

For non-compliant peers (i.e. just about everything) this should have no
effect.

Free generated supp data after handshake completion, add comment regarding use of num_renegotiations in TLS and supp data generation callbacks

Add callbacks supporting generation and retrieval of supplemental data entries, facilitating RFC 5878 (TLS auth extensions)
Removed prior audit proof logic - audit proof support was implemented using the generic TLS extension API
Tests exercising the new supplemental data registration and callback api can be found in ssltest.c.
Implemented changes to s_server and s_client to exercise supplemental data callbacks via the -auth argument, as well as additional flags to exercise supplemental data being sent only during renegotiation.

 * Many XMPP servers are configured with multiple domains (virtual hosts)
 * In order to establish successfully the TLS connection you have to specify
   which virtual host you are trying to connect.
 * Test this, for example with ::
   * Fail:
       openssl s_client -connect talk.google.com:5222 -starttls xmpp
   * Works:
       openssl s_client -connect talk.google.com:5222 -starttls xmpp -xmpphost gmail.com

 * When the host used in "-connect" is not what the remote XMPP server expects
   the server will return an error like this:
     <stream:error>
       <host-unknown xmlns='urn:ietf:params:xml:ns:xmpp-streams'/>
     </stream:error>
 * But the actual code will stay on the loop forever because the stop condition
   "/stream:features>" will never happen,
 * Make this more robust: The stop condition should be that BIO_read failed
 * Test if for example with ::

    openssl s_client  -connect random.jabb3r.net:5222 -starttls xmpp

 * Some XMPP Servers (OpenFire) use double quotes.
 * This makes s_client starttls work with this servers.
 * Tested with OpenFire servers from http://xmpp.net/ ::

     openssl s_client -connect coderollers.com:5222 -starttls xmpp

OS X 10.8..10.8.3 has broken support for ECDHE-ECDSA ciphers.

(cherry picked from commit 90e7f983)

Preliminary documentation for chain and verify stores and certificate chain
setting functions.