Just "packed" doesn't always pack the way we expect.

	(grub_scsi_read_capacity10): ... this.
	(grub_scsi_read_capacity16): New function.
	(grub_scsi_open): Use read_capacity16 if read_capacity10 returned
	0xffffffff.
	Fix off-by-one error.
	* include/grub/scsi.h (grub_scsi): Rename size to last_block and make it
	64-bit unsigned.
	* include/grub/scsicmd.h (grub_scsi_read_capacity): Rename to ...
	(grub_scsi_read_capacity10): ... this.
	(grub_scsi_read_capacity_data): Rename to ...
	(grub_scsi_read_capacity10_data): ... this. Rename size to last_block.
	(grub_scsi_read_capacity16): New struct.
	(grub_scsi_read_capacity16_data): Likewise.
	(grub_scsi_cmd_t): Rename grub_scsi_cmd_read_capacity to
	grub_scsi_cmd_read_capacity10.
	New command grub_scsi_cmd_read_capacity16.

	* grub-core/disk/scsi.c (grub_scsi_read16): New function.
	(grub_scsi_write16): Likewise.
	(grub_scsi_read): Use read16 when necessary.
	(grub_scsi_write): Likewise.
	* include/grub/scsicmd.h (grub_scsi_read16): New struct.
	(grub_scsi_write16): Likewise.
	(grub_scsi_cmd_t): Add READ16 and WRITE16.

	* conf/common.rmk (pkglib_MODULES): Add scsi.mod.
	(scsi_mod_SOURCES): New variable.
	(scsi_mod_CFLAGS): Likewise
	(scsi_mod_LDFLAGS): Likewise.

	* disk/scsi.c: New file.

	* include/grub/scsi.h: Likewise.

	* include/grub/scsicmd.h: Likewise.

	* disk/ata.c: Include <grub/scsi.h>.
	(grub_atapi_packet): Do not use grub_ata_cmd, use registers
	instead.
	(grub_ata_iterate): Skip ATAPI devices.
	(grub_ata_open): Only handle ATAPI devices.
	(struct grub_atapi_read): Removed.
	(grub_atapi_readsector): Likewise.
	(grub_ata_read): No longer handle ATAPI devices.
	(grub_ata_write): Likewise.
	(grub_atapi_iterate): New function.
	(grub_atapi_read): Likewise.
	(grub_atapi_write): Likewise.
	(grub_atapi_open): Likewise.
	(grub_atapi_close): Likewise.
	(grub_atapi_dev): New variable.
	(GRUB_MOD_INIT(ata)): Register ATAPI as SCSI device.
	(GRUB_MOD_FINI(ata)): Unregister ATAPI.

	* include/grub/disk.h (enum grub_disk_dev_id): Add
	`GRUB_DISK_DEVICE_SCSI_ID'.