coreutils: bump version

Coreutils 6.9 was broken with glibc >= 2.6, due to a coreutils
internal function being named like a glibc function. This has been
fixed in more recent coreutils version, by
http://lists.pld-linux.org/mailman/pipermail/pld-cvs-commit/Week-of-Mon-20070514/155466.html

.

Therefore, we upgrade coreutils to its latest version, 7.4, which
raised two problems:

 * Recent coreutils releases are not anymore available as .bz2
   archives, only .xz archives. Since this archive format is not
   supported by Buildroot yet, and the corresponding tools are not
   widely available yet, we fallback to the bigger .gz format for the
   coreutils package.

 * The rename bug detection script m4/rename.m4 was broken, leading
   coreutils to try to include windows.h and compile some
   Windows-specific code. We introduce a patch to fix this, patch
   which has been taken from gnulib. We also make sure that this
   workaround is nevery compiled in by passing
   gl_cv_func_rename_dest_exists_bug=no to the configure script.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>