r17179: Merge the vl-posixacls tmp branch into mainline. It

r17179: Merge the vl-posixacls tmp branch into mainline. It
modularizes our interface into the special posix API used on
the system. Without this patch the specific API flavor is
determined at compile time, something which severely limits
usability on systems with more than one file system. Our
first targets are AIX with its JFS and JFS2 APIs, at a later
stage also GPFS. But it's certainly not limited to IBM
stuff, this abstraction is also necessary for anything that
copes with NFSv4 ACLs. For this we will check in handling
very soon.

Major contributions can be found in the copyright notices as
well as the checkin log of the vl-posixacls branch. The
final merge to 3_0 post-3.0.23 was done by Peter Somogyi
<psomogyi@gamax.hu>
(This used to be commit ca0c73f281a2a65a988094a46bb3e46a94011a53)