Added changes between version 55163.44 and 55471 to function SSLVerifySignedServerKeyExchange.

Source for 55163.44: <https://github.com/Apple-FOSS-Mirror/Security/blob/master/libsecurity_ssl/lib/sslKeyExchange.c>
Source for 55471: <http://opensource.apple.com/source/Security/Security-55471/libsecurity_ssl/lib/sslKeyExchange.c?txt>

55471 = #gotofail