(grub_ofdisk_open): Use it to un-escape "," characters.
* kern/disk.c (find_part_sep): New.
(grub_disk_open): Use it to find the first non-escaped ','
character in the disk name.
* util/ieee1275/devicemap.c (escape_of_path): New.
(grub_util_emit_devicemap_entry): Use it.
* util/sparc64/ieee1275/grub-install.in: Update script to
strip partition specifiers properly by not triggering on
'\' escaped ',' characters.