[xml] IDREF/IDREFS attribute are not validated in xml Schema or RelaxNG

[GUY Fabrice <fabrice guy gmail com>]

Hi,

I don't know if it's in the TODO list or if it's a bug, but IDREF (and
IDREFS) are not validated using xmlSchema or RelaxNG : if an IDREF
attribute has a value which is not carried by an ID attribute, the
document still validates.

I can provide a test case if you want some.

Regards,

Fabrice