Bit shifts should be done on unsigned type as a matter of good practice
to avoid any problems with bit overflowing to the sign bit.
Signed-off-by: David Sterba <dsterba@suse.com>
The crc32c.c is going to be updated with CPU feature detection from
common/ which is not suitable for libbtrfs, so make own copy of the
file.
Signed-off-by: David Sterba <dsterba@suse.com>