search in Info should not find "File", "Node" etc. in header

[Drew Adams]

Search for "file" in Info. it finds each occurrence of "File" at the
top of each node. This text is _not_ part of the Info text, and it
should _not_ be found. This makes it impossible to search for "file"
(or "node" or...), which is an important keyword to be able to search
for.

In GNU Emacs 21.3.50.1 (i386-mingw-nt5.1.2600)
 of 2004-07-26 on BERATUNG4
configured using `configure --with-gcc
(3.3) --cflags -I../../jpeg-6b-1/include -I../../libpng-1.2.4-1/include -I..
/../tiff-3.5.7/include -I../../xpm-nox-4.2.0/include -I../../zlib-1.1.4-1/in
clude'