[xmlsec] Retrieving the X509 certificate from a signed XML file.

[Aleksey Sanin]

The signature key is returned in the xmlSecDSigCtx structure
as "signKey":

http://www.aleksey.com/xmlsec/api/xmlsec-xmldsig.html#XMLSECDSIGCTX

Inside xmlSecKey there is a list of xmlSecKeyData objects "dataList"
and X509 certificate is one of these objects:

http://www.aleksey.com/xmlsec/api/xmlsec-keys.html#XMLSECKEY


Aleksey