Make this do the right thing with entries which start with the percent sign,

Make this do the right thing with entries which start with the percent sign,
in response to Skip's comments in SF bug #487165.

Make use of string methods instead of string module functions in most places.
Add (and make the default) a way to collapse symbol entries into a single
"Symbols" section in the generated index.  This is similar to what makeindex
does, but does not include entries beginning with an underscore.