Bernard,
The xmlns:xlink declaration is required. See the SVG spce, section
5.3.2:
"In all cases, for compliance with the "Namespaces in XML"
Recommendation [XML-NS], an explicit XLink namespace
declaration must be provided whenever one of the above XLink attributes
is used within SVG content.
Testing my own SVG renderer I am use to
compare my outputs to yours with the joined file I got the following
results: - Adobe blank output - eSVG black output -
WebDraw as my output seems ok - CSIRO blank output - Batik
Attribute xlink:href on is required problem with
namespace support?