Given a piece of stexi, return an index of a specified variety.
Note that currently, stexi-extract-index doesn't differentiate between
different kinds of index entries. That's a bug ;)
Given an stexi tree tree, index all of the entries of type kind. kind can be one of the predefined texinfo indices (
concept,variable,function,key,program,type) or one of the special symbolsautoorall.autowill scan the stext for a(printindex)statement, andallwill generate an index from all entries, regardless of type.The returned index is a list of pairs, the car of which is the entry (a string) and the cdr of which is a node name (a string).