24:00:00 in time and dateTime values

Background

See background in version2#487 (closed).

Short summary: the time "24:00:00" is valid according to the XML specification, but is not accepted by MS .NET.

Three alternative solutions

1. Syntactically exclude "24:00:00" for any xs:time or xs:dateTime value, by adding a pattern restriction.
2. Warn that "24:00:00" for any xs:time or xs:dateTime value is not compatible with MS .NET and should be avoided.
3. Do nothing.

If implementing solution 1 or 2, a warning (like the one in solution 2) should probably also be added to existing railML versions.