* DISTLIST: Add util/update-grub.in, util/grub.d/00_header.in,
	util/grub.d/10_hurd.in, util/grub.d/10_linux.in and util/grub.d/README.
	* Makefile.in: Build update-grub_SCRIPTS.  Install update-grub_SCRIPTS
	and update-grub_DATA.
	* conf/common.rmk: Build and install update-grub components.
	* conf/common.mk: Regenerate.
	* util/update-grub.in: New.  Core of update-grub.
	* util/grub.d/00_header.in: New.  Generates grub.cfg header.
	* util/grub.d/10_hurd.in: New.  Generates boot entries for the Hurd.
	* util/grub.d/10_linux.in: New.  Generates boot entries for Linux.
	* util/grub.d/README: New.  Document grub.d directory layout.