[xcbf] References

Due to agreements made in Baltimore, I'll add the following to the
XCBF document,

– ITU-T Recommandation X.693 (2002) / Amd.1 (2003) | ISO/IEC 
8825-4:2002/Amd.1:2003, Information technology – ASN.1 encoding rules: 
XML Encoding Rules (XER) – Amendment 1: XER Control Notation (XCN) and 
Variable XER (VXER).

This will cover our use of Base64 armoring of X.509 certificates and CRLs.

Phil