Extended Attributes for ext 2/3 filesystems

Hi Linus,

This is a resend of the extended attributes and ACL patches for ext2/3. They are updated against bk-current, with a minor fix in fs/Config.in. No comments were made against the last time I submitted these patches, and the patches are relatively low risk, as they don't significantly change the code paths if the extended attribute and ACL configs are not defined.

I believe they are ready to be applied to the main tree.

- Ted