Support for El Torito without floppy emulation.
* util/mkisofs/eltorito.c: Include `<errno.h>'.
(init_boot_catalog): Improve error handling.
(get_torito_desc): Don't use floppy emulation unless requested by
user. Patch boot information table when requested via
`-boot-info-table'.
* util/mkisofs/iso9660.h (struct eltorito_boot_info): New struct.
* util/mkisofs/mkisofs.c (use_eltorito_emul_floppy)
(use_boot_info_table): New variables.
(OPTION_BOOT_INFO_TABLE, OPTION_NO_EMUL_BOOT)
(OPTION_ELTORITO_EMUL_FLOPPY): New macros.
(ld_options): Handle `-boot-info-table', `-no-emul-boot' and
`--eltorito-emul-floppy'.
(main): Handle `OPTION_BOOT_INFO_TABLE', `OPTION_NO_EMUL_BOOT'
and `OPTION_ELTORITO_EMUL_FLOPPY'.
* util/mkisofs/mkisofs.h (use_eltorito_emul_floppy)
(use_boot_info_table, get_731): New prototypes.
* util/mkisofs/write.c (get_731): New function.
