If I choose index in the top 'menu' libc-info-file, I am given a page
about an index function regarding strings, not the index I was supposing
with a list of all functions/variables.

When I press 'u' I get to where I want.. 

Ahh well ntemacs 19.34 win95.. 

This is a known bug in the libc docs; they don't have a properly defined 'index'
node.  I ran into a similar problem when trying to create an info lookup function
for Emacs.