SSL: use faster SSL ciphers

I am not sure this is much of a gain, but we might want to research it anyway:

The preferred cipher suite of Qt is TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA
(0xc014) . Google sites often choose TLS_ECDHE_RSA_WITH_RC4_128_SHA (0xc011)
because it is quite fast and does not need padding.
Assuming that most sites still use a 1024 bit public key (can anyone comfirm?),
apparently using AES256 is overkill (i.e. breaking the public key is far easier
than breaking the symmetric key).

So maybe we want to check whether preferring the RC4 ciphersuite and the AES128
ones over the AES256 one is faster.

Here is an interesting read:
http://www.imperialviolet.org/2010/06/25/overclocking-ssl.html