XZ CRC64 and SHA256 support.

	XZ CRC64 and SHA256 support.

	* Makefile.util.def (libgrubmods): Add crc64.c.
	* grub-core/Makefile.core.def (crc64): New module.
	* grub-core/lib/crc64.c: New file.
	* grub-core/lib/xzembed/xz_dec_stream.c (xz_dec_hash)
	[!GRUB_EMBED_DECOMPRESSOR]: Rename crc32_context to hash_context.
	Fix the type.
	(MAX_HASH_SIZE): New define.
	(xz_dec) [!GRUB_EMBED_DECOMPRESSOR]: Add generic hash fields.
	(dec_block) [!GRUB_EMBED_DECOMPRESSOR]: Handle non-crc32 hashes.
	(index_update) [!GRUB_EMBED_DECOMPRESSOR]: Likewise.
	(dec_index) [!GRUB_EMBED_DECOMPRESSOR]: Likewise.
	(crc32_validate) [!GRUB_EMBED_DECOMPRESSOR]: Rename to ...
	(hash_validate) [!GRUB_EMBED_DECOMPRESSOR]: ... this.
	Handle non-crc32 hashes.
	(hashes) [!GRUB_EMBED_DECOMPRESSOR]: New variable.
	(dec_stream_header): Handle non-crc32 hashes.
	(dec_stream_footer): Likewise.
	(dec_block_header): Likewise.
	(dec_main): Likewise.
	(xz_dec_init): Likewise.
	(xz_dec_reset): Likewise.
	(xz_dec_end): Likewise.
	* util/import_gcry.py: Add CRC64 line.