Make the format of Environment Block plain text. The boot loader
part is not tested well yet.
* util/grub-editenv.c (DEFAULT_ENVBLK_SIZE): New macro.
(buffer): Removed.
(envblk): Likewise.
(usage): Remove "info" and "clear". Add "unset". Update the
description of "set", as this does not delete variables any
longer.
(create_envblk_file): Complete rewrite.
(open_envblk_file): Likewise.
(cmd_info): Removed.
(cmd_list): Likewise.
(cmd_set): Likewise.
(cmd_clear): Likewise.
(list_variables): New function.
(write_envblk): Likewise.
(set_variables): Likewise.
(unset_variables): Likewise.
(main): Complete rewrite.
* commands/loadenv.c (buffer): Removed.
(envblk): Likewise.
(open_envblk_file): New function.
(read_envblk_file): Complete rewrite.
(grub_cmd_load_env): Likewise.
(grub_cmd_list_env): Likewise.
(struct blocklist): New struct.
(free_blocklists): New function.
(check_blocklists): Likewise.
(write_blocklists): Likewise.
(grub_cmd_save_env): Complete rewrite.
* include/grub/lib/envblk.h (GRUB_ENVBLK_SIGNATURE): Replaced with
a plain text signature.
(GRUB_ENVBLK_MAXLEN): Removed.
(struct grub_envblk): Complete rewrite.
(grub_envblk_find): Removed.
(grub_envblk_insert): Likewise.
(grub_envblk_open): New prototype.
(grub_envblk_set): Likewise.
(grub_envblk_delete): Put const to VALUE.
(grub_envblk_iterate): Put const to NAME and VALUE.
(grub_envblk_close): New prototype.
(grub_envblk_buffer): New inline function.
(grub_envblk_size): Likewise.
* lib/envblk.c: Include grub/mm.h.
(grub_env_find): Removed.
(grub_envblk_open): New function.
(grub_envblk_close): Likewise.
(escaped_value_len): Likewise.
(find_next_line): Likewise.
(grub_envblk_insert): Removed.
(grub_envblk_set): New function.
(grub_envblk_delete): Complete rewrite.
(grub_envblk_iterate): Likewise.
