Investigate index generation exemplar alignment for radicals 丬 and 卤 in implicithan mode

[hsivonen]

In case we decide to support collation index functionality in the future, leaving this note to investigate: For radicals 丬 and 卤 the boundary reference character is not in the original unified ideograph block. Figure out how this interacts with the insertion of index markers into the *-u-co-unihan tailorings.

That is, do the index markers work only with the full unihan root, or do they work for the original unified ideograph block, including characters whose radical is 丬 or 卤, with the implicithan root?