Return a list of elements which are allowable targets for a link. This list primarily expresses those elements which this stylesheet is able to generate a link to -- it's more to do with this stylesheet's capabilities than with any fundamental property of the document type.
This will be used when linking to (an ID attribute within) an object which can't be linked to directly. It doesn't matter if there's redundancy in this -- the appropriate element is selected as the first member of this list amongst the target element's ancestors.
Note that we include "routine" in the list, even though that element doesn't appear in the General DTD, so that links to routines from that DTD must be done via the coderef element. This allows us to link within a programcode element, to other elements within the same document. There is currently no means of referring, from a programcode document, to elements in another programcode document.
The link text will be generated by function
(make-section-reference).
For example, the LABEL element in the DocumentSummary DTD requires this.
Type: list of strings
List of allowable link targets