Renaming an Index node to prevent file collision

[Michael Hope]

Hi there.  There's been a discussion[1] going on on the GDB list about
cross building manuals for case insensitive filesystems.  At Linaro we
use a Linux host to cross build a Windows binary of GCC and GDB[2].
makeinfo runs on a Linux host and generates index.html for the Top
node and Index.html for the Index node.  These differ only in case and
cause trouble when you later try to install them in Windows.

This has come up a few times over the last four years:
 http://sourceware.org/ml/gdb-patches/2010-11/msg00431.html
 http://sourceware.org/ml/gdb-patches/2009-01/msg00298.html

and has been discussed on this list:
 http://lists.gnu.org/archive/html/bug-texinfo/2008-12/msg00012.html
 http://lists.gnu.org/archive/html/bug-texinfo/2010-11/msg00033.html

There's at least three groups working around the problem in their
build systems which is unfortunate.

The current Top to index.html mapping is in nodename_to_filename_1().
One fix is to special case nodes called 'Index' in the same way and
rename them to 'Index_.html'.  This keeps the problematic names in one
place.

Shall I send a patch?

-- Michael
[1] http://sourceware.org/ml/gdb-patches/2012-06/msg00457.html
[2] https://launchpad.net/linaro-toolchain-binaries