gfs2: use generic posix ACL infrastructure

This contains some major refactoring for the create path so that
inodes are created with the right mode to start with instead of
fixing it up later.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --cc fs/gfs2/acl.c
Simple merge

diff --cc fs/gfs2/acl.h
Simple merge

diff --cc fs/gfs2/inode.c
Simple merge

diff --cc fs/gfs2/xattr.c
Simple merge