xfs: B+Tree GetNext() works

The GetNext() works well for B+Trees and that wraps up the work needed
for all kinds of GetNext().
Change-Id: Ie965d3da273364f8fdbdb8faee5cb3c214881130
Reviewed-on: https://review.haiku-os.org/c/haiku/+/3124
Tested-by: Commit checker robot <no-reply+buildbot@haiku-os.org>
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

xfs: Reading Inodes

This patch successfully reads inodes. There are also some style fixes.
The inodes aren't published and some useful hooks are yet to implement.

Change-Id: I73e6c68f1c2177871fbd0b241a67826aea1b17be
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2738
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

Adding superblock, types, xfs_mount and volume

Superblock work is done. A valid superblock is now detected.
xfs_shell will fail though, because the filesystem does not own it's
root node.

Change-Id: I78e3c21c4d0dd8e535fd24df4a0c107ed5fb201c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2286
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

Making of xfs file system

xfs_shell is modeled over bfs_shell.
It fails to mount the filesystem as expected
(the filesystem code isn't implemented).

Change-Id: Iaf88c1f4aef338f249fdc58bc27a3ad76ebd5d95
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2096
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>