hfsplus: add necessary declarations for POSIX ACLs support

This patchset implements POSIX ACLs support in hfsplus driver.

Mac OS X beginning with version 10.4 ("Tiger") support NFSv4 ACLs, which
are part of the NFSv4 standard.  HFS+ stores ACLs in the form of
specially named extended attributes (com.apple.system.Security).

But this patchset doesn't use "com.apple.system.Security" extended
attributes.  It implements support of POSIX ACLs in the form of extended
attributes with names "system.posix_acl_access" and
"system.posix_acl_default".  These xattrs are treated only under Linux.
POSIX ACLs doesn't mean something under Mac OS X.  Thereby, this patch
set provides opportunity to use POSIX ACLs under Linux on HFS+
filesystem.

This patch:

Add CONFIG_HFSPLUS_FS_POSIX_ACL kernel configuration option, DBG_ACL_MOD
debugging flag and acl.h file with declaration of essential functions
for support POSIX ACLs in hfsplus driver.

Signed-off-by: Vyacheslav Dubeyko <slava@dubeyko.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Hin-Tak Leung <htl10@users.sourceforge.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>