[xmlsec] Using X509Data as key format

[Aleksey Sanin]

> Is it true that xmlSecMSCryptoKeyDataX509Klass.objSize is
> xmlSecMSCryptoX509DataSize? It seems to cause the problem I get.
> 
> It's less then xmlSecMSCryptoKeyDataSize...
> 
Yes, xmlSecMSCryptoX509DataSize.objSize defines the size of
xmlSecMSCryptoX509Data structures. The xmlSecMSCryptoX509DataSize
is "derived" from xmlSecKeyData thus it should have at least
the same size.

Aleksey