[docbook] Infocenter link (xlink:hef=) to PLUGINS_ROOT/plugin.id.here/filename.html%23nameofanXMLID goes to top of page

[mrodger]

Using Docbook5, Eclipse 3.4.2, with each individual book as a plugin in an
infocenter.

I can link from book to book (plugin to plugin) only to the file. Let¹s say
filename.html is a lengthy topic and I want to link to the 10th paragraph
(<para xml:id=²nameofanXMLID²).