bug#1118: 23.0.60; Info claims no index exists if first instance of an info file is visited via info-lookup-symbol

[martin rudalics <rudalics@gmx.at>]

 > In GNU Emacs 23.0.60.4 (i686-pc-linux-gnu, X toolkit, Xaw3d scroll bars)
 >  of 2008-10-07 on lamacq.ph.ed.ac.uk
 > Windowing system distributor `The X.Org Foundation', version 11.0.60802000
 > configured using `configure  '-C' '--prefix=/scratch/s0198183/applications/emacs-trunk/' 'CFLAGS=-ggdb3 -O0' '--without-rsvg''
 >
 > emacs -Q
 > C-h i d m Elisp RET
 > i set-text-properties RET
 >
 > takes me to the set-text-properties entry in the Elisp manual (as
 > expected).
 >
 > emacs -Q
 > C-h S add-text-properties RET ; use info-look to find add-text-properties
 > C-x b *info* RET              ; switch to info buffer
 > i                             ; try to lookup something in the index
 >
 > complains "No index"

FWIW, it's due to this change

2008-06-15  Juri Linkov  <juri@jurta.org>

	* info.el (Info-toc): Call Info-toc-nodes instead of Info-build-toc.
	(Info-toc, Info-insert-toc): Increment nth's index to add PARENT
	as the second element.
	(Info-build-toc): Add PARENT element extracted from the Up pointer.
	Don't print progress messages.
	(Info-toc-nodes): New variable and function.
	(Info-index-nodes): Optimize non-string file name case.
	^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
	
Juri, please have a look.

martin