[xmlsec] core methods for write of <X509SubjectName/> and <X509IssuerSerial/>

[Aleksey Sanin]

>
> O.K.
> but when <X509Data/> in template contain child nodes some XXXXRead 
> methods fails.
> This happen beffore call of xmlSecOpenSSLKeyDataX509XmlWrite(...).
> At momment I can put only <X509SubjectName/> in  <X509Data/> without 
> XXXXRead to fail.
>
Well, probably the code in the xmlSecOpenSSLX509CertificateNodeRead() 
and friends
needs to be smart enough to do not print an error if the node content is 
empty and just skip
it instead.

Aleksey