aufs: describe several optional patches

aufs3-loopback.patch has existed since many years before, but not
described. Other two patches are introdued by the neighbourhood of this
commit.

Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
Merge remote-tracking branch 'aufs3-standalone/aufs3.9/00base' into aufs3.9/10static
Merge branch 'aufs3.9/10static' into aufs3.9/11proc_map
aufs: add a postscript about mainline-ing

Signed-off-by: J. R. Okajima <hooanon05g@gmail.com>
Merge branch 'aufs3.9/00base' into aufs3.10/00base
Merge remote-tracking branch 'aufs3-standalone/aufs3.9/00base' into aufs3.9/10static
Merge branch 'aufs3.9/10static' into aufs3.9/11proc_map
Merge branch 'aufs3.9/10static' into aufs3.10/10static
Merge remote-tracking branch 'aufs3-standalone/aufs3.10/00base' into aufs3.10/10static
Merge branch 'aufs3.9/11proc_map' into aufs3.10/11proc_map
Merge branch 'aufs3.10/10static' into aufs3.10/11proc_map
Merge branch 'aufs3.10/00base' into aufs3.11/00base
Merge branch 'aufs3.11/00base' into aufs3.12/00base
Merge branch 'aufs3.12/00base' into aufs3.13/00base
Merge branch 'aufs3.10/10static' into aufs3.11/10static
Merge remote-tracking branch 'aufs3-standalone/aufs3.11/00base' into aufs3.11/10static
Merge branch 'aufs3.10/11proc_map' into aufs3.11/11proc_map
Merge branch 'aufs3.11/10static' into aufs3.11/11proc_map
Merge branch 'aufs3.11/10static' into aufs3.12/10static
Merge remote-tracking branch 'aufs3-standalone/aufs3.12/00base' into aufs3.12/10static