aufs-util: new package

Signed-off-by: Christian Stewart <christian@paral.in>
[Atul:
 - Updated the default to empty.
 - Updated the license to GPLv2.
 - Used patches instead of SED commands.
 - CC and LD are replaced by TARGET_CC and TARGET_LD.]
Signed-off-by: Atul Singh <atul.singh.mandla@rockwellcollins.com>
[yann.morin.1998@free.fr:
  - drop the headers_install command
  - instead, instruct the kernel to install them
  - add patches 0002..0004
  - properly build the host tools
  - don't depend on the aufs extension, for kernel already patched
  - fix comment]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
[Thomas:
 - Remove the patch 0004-no-override-readdir64.patch, since it no longer
   applies to the latest version of aufs-util. Instead, add a post-patch
   hook that tweaks the Makefile to remove the problematic rdu64.o from
   the build process.
 - Use directly the kernel headers from the kernel source tree, rather
   than having to install them. This only requires a minor trick to
   define "__user" to empty.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>