GDP: index entries for snippets

[Graham Percival]

Latest GDP docs
http://web.uvic.ca/~gperciva/

(although these are almost identical to the 2.11.39 docs at the
moment)


Do we want index entries for snippets?  For example, in
  NR 1.1.3.2 Key signature
there are two snippets: suppressing natural signs in key
signatures, and non-standard key signatures.

Do you want to have items like:
@cindex key signatures, suppressing natural signs
@cindex don't print natural signs in key signatures
@cindex key signatures, non-standard
@cindex key signatures, whole tone

pointing to these?  Adding index entries for all the snippets
increases the amount of work that we need to do on each doc
section, of course.

I'm personally not convinced that these are necessary -- after
all, if a user can't find "key signature" in the index, he won't
be able to find "key signature, suppressing natural signs".  And
if he _is_ looking a way to avoid printing natural signs in key
signatures, I think he'd look at "key signatures" even if there
wasn't a "key signature, suppressing natural signs" entry.


More examples are in
  NR 1.2.1.2 Tuplets

such as
@funindex tupletNumberFormatFunction
@funindex tupletSpannerDuration
and
@cindex tuplet bracket length
@cindex triplet bracket length
@cindex bracket length, tuplets


Of course, I famously never use the index, so I'm not the best
person to judge whether certain index entries are helpful or not.
Discuss.

Cheers,
- Graham