ocfs2: Add the underlying blockcheck code.

ocfs2: Add the underlying blockcheck code.

This is the code that computes crc32 and ecc for ocfs2 metadata blocks.
There are high-level functions that check whether the filesystem has the
ecc feature, mid-level functions that work on a single block or array of
buffer_heads, and the low-level ecc hamming code that can handle
multiple buffers like crc32_le().

It's not hooked up to the filesystem yet.

Signed-off-by: Joel Becker <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Signed-off-by: Mark Fasheh <[email protected]>