#29 both CRC32C and Posix CRC32 (ethernet) needed

[Charles Evans]

iSCSI uses CRC32C because
Posix CRC32 is not very effective for large files (>65k)
CRC32C is effective for files up to about 2G
(see http://www.rfc-editor.org/rfc/rfc3385.txt )
Please provide both.
Thanks.

CRC32C may be used by BTRFS
i7 CPU has CRC32C instruction