incorrect HTML.index output

Hi,

I just noticed that on bookindex.html, we have this entry:

π, Mathematical Functions and Operators

This is an entry for "pi".  In the HTML it looks like
π, Mathematical Functions and Operators

So the actual problem is that we're escaping the & twice.  The problem
is in HTML.index, which looks like this:

INDEXTERM functions-math.html
INDEXPOINT functions-math.html#AEN6970
TITLE Mathematical Functions and Operators
significance NORMAL
PRIMARY π
/INDEXTERM

However, it's not as easy as disabling the escape of &, because we also
have this entry:

INDEXTERM functions-textsearch.html#FUNCTIONS-TEXTSEARCH-TSQUERY
INDEXPOINT functions-textsearch.html#AEN13687
TITLE tsquery
significance NORMAL
PRIMARY TSQUERY && TSQUERY
/INDEXTERM

So these & must be escaped, otherwise this operator wouldn't be
displayed correctly.

I'm unsure what to do about it.  To me, the simplest solution seems to
be to just remove the index entry.

--
Alvaro Herrera                        http://www.advogato.org/person/alvherre
Major Fambrough: You wish to see the frontier?
John Dunbar: Yes sir, before it's gone.