XML Dsig schema reference

["Conor P. Cahill" <concahill@aol.com>]

Within the core schema, the XML DSig schema is imported using a
reference to the W3C page that will always return the "latest" version
of the specification (what I would call an "undated" reference):

http://www.w3.org/TR/xmldsig-core/xmldsig-core-schema.xsd

I recommend that this be changed to a dated reference to a specific
version of the XMLDsig specification for several reasons including a)
the current setting causes problems in some validators when other
specifications include the date specific version and b) the TC
tested/approved a specific version of the standard and would need to
review any updated standard before adopting it.  The dated version of
the reference would be:

http://www.w3.org/TR/2002/REC-xmldsig-core-20020212/xmldsig-core-schema.xsd

The resulting change is zero with respect to functionality/schema
details as they both refer to the same file contents, so I would think
this simply an editorial change that protects against potential problems
should the dsig spec evolve.

Conor