This patch fixes two integer underflows at:
  * grub-core/lib/crypto.c
  * grub-core/normal/auth.c

CVE-2015-8370
Signed-off-by: Hector Marco-Gisbert <hecmargi@upv.es>
Signed-off-by: Ismael Ripoll-Ripoll <iripoll@disca.upv.es>
Also-By: Andrey Borzenkov <arvidjaar@gmail.com>

All current ciphers have blocks which are power of 2 and it's
unlikely to change. Other block length would be tricky to handle anyway.
This restriction allows avoiding extra divisions.

	array.

	length arrays.

	windows variant.
	* util/grub-mkpasswd-pbkdf2.c: Add windows flavour for retrieving random
	data.

	on it.

	* grub-core/disk/raid.c (grub_raid_block_xor): Removed. All users
	changed to grub_crypto_xor
	* grub-core/lib/crypto.c (grub_crypto_xor): Moved from here ...
	* include/grub/crypto.h (grub_crypto_xor): ... here. Inlined.
	Use bigger types when possible.

	guidelines.

	* grub-core/kern/dl.c (grub_dl_check_license): New function.
	(grub_dl_load_core): Use grub_dl_check_license.
	* include/grub/dl.h (GRUB_MOD_SECTION): New macro.
	(GRUB_MOD_LICENSE): Likewise.
	(GRUB_MOD_DUAL_LICENSE): Likewise.
	All modules updated.

Use dedicated simple password retriever for size of future crypto disks modules and simplify entering passwords routines