* kernel/disk.c (grub_disk_read): Use void pointer for the
buffer.
(grub_disk_write): Use const void pointer for the buffer.
Adjust all callers. Remove unnecessary casts.
Parttool autoloading and improvements
* Makefile.in (pkglib_DATA): add parttool.lst
(parttool.lst): new target
* genmk.rb: generate parttool-*
(CLEANFILES): add #{parttool}
(PARTTOOLFILES): new variable
* genparttoollist.sh: new file
* parttool/pcpart.c (grub_pcpart_boot): more feedback
(grub_pcpart_type): likewise
* commands/parttool.c (helpmsg): new variable
(grub_cmd_parttool): output help if not enough arguments are supplied
autoload modules
(GRUB_MOD_INIT(parttool)): use helpmsg
