Index.html doesn't fold on case insensitive filesystems

[Yuan Fu]

I tried to export texinfo to HTML for Emacs Lisp Reference Manual. And it has 
an index page. According to the manual makeinfo should fold the index.html and 
Index.html. However I only see the content of Index.html. 

I also tried to set CASE_INSENSITIVE_FILENAMES to true, but that didn’t make 
any difference.

How should this work in general on case insensitive filesystems? Thanks.

Yuan