Update btrfs compression types, add ZSTD, drop LAST

Signed-off-by: Timofey Titovets <nefelim4ag@gmail.com>

include/crucible/fs.h

@@ -112,8 +112,8 @@ namespace crucible {
 		BTRFS_COMPRESS_NONE  = 0,
 		BTRFS_COMPRESS_ZLIB  = 1,
 		BTRFS_COMPRESS_LZO   = 2,
-		BTRFS_COMPRESS_TYPES = 2,
-		BTRFS_COMPRESS_LAST  = 3,
+		BTRFS_COMPRESS_ZSTD  = 3,
+		BTRFS_COMPRESS_TYPES = 3
 	} btrfs_compression_type;
 
 	struct FiemapExtent : public fiemap_extent {