FSAL/creds : backport of Frank's functions using __NR_setgroups syscall.
Functions set_credentials() and set_creds_to_root() are located in src/FSAL/fsal_commonlib.c
capset()/capget() area of the code is now '#ifdef LINUX' bracketed.
Rebase to dev_18
Rebase on dev_19
This patch fixes the regression in _9p_readlink() found via cthon04/basic/test8
Patch proposal : prevent test_access to deny aithorized access as open( O_CREAT, 04XY ) is performed