2009-04-27 Vladimir Serbinenko <phcoder@gmail.com>

2009-04-27  Vladimir Serbinenko <phcoder@gmail.com>

	Preboot hooks support

	* commands/boot.c (struct grub_preboot_t): new declaration
	(preboots_head): new variable
	(preboots_tail): likewise
	(grub_loader_register_preboot_hook): new function
	(grub_loader_unregister_preboot_hook): likewise
	(grub_loader_set): launch preboot hooks
	* include/grub/loader.h (grub_loader_preboot_hook_prio_t): new type
	(grub_loader_register_preboot_hook): new declaration
	(grub_loader_unregister_preboot_hook): likewise