Adds the HTML class "rda264" to the span generated by the XSLT function
showRDAtag264.
To test, same as previous, using a notice with a 264 tag. Both patches
only apply to MARC21.
I was unsure how to name the class, so I've chose the simplest, most
explicit name.
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de> Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl> Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>