[COMMITTED] Remove references to non-existent content items in install.texi

[Joseph S. Myers]

On Fri, 27 Sep 2013, Allan McRae wrote:

> This fixes the regeneration of the INSTALL file with texinfo-5.x,
> although using this version will result in lots of formatting changes
> to the generated INSTALL file (mainly quote and url formatting).

This breaks "make install" for me with makeinfo 4.13.  I get a sequence of 
errors starting with:

LANGUAGE=C LC_ALL=C makeinfo -P /home/jsm28/tmp/tmpdir/glibc/build-64/manual/ --output=/home/jsm28/tmp/tmpdir/glibc/build-64/manual/libc.info libc.texinfo
/home/jsm28/tmp/tmpdir/glibc/libc/manual//header.texi:1: Next reference to nonexistent node `Installation' (perhaps incorrect sectioning?).
[...]
makeinfo: Removing output file `/home/jsm28/tmp/tmpdir/glibc/build-64/manual/libc.info' due to errors; use --force to preserve.
make[2]: *** [/home/jsm28/tmp/tmpdir/glibc/build-64/manual/libc.info] Error 1

-- 
Joseph S. Myers
joseph@codesourcery.com