Summary: remove the 16 groups limit in the NFS client

This directory contains the many-groups patch split into separate
parts. Patch 41, 45 and 50 change behavior already because the code path
does not go through the nfs?_proc_<op> functions. That's why there is a
test on the NFS version there as well: prevent any effects on NFSv4 (it
wouldn't harm because the situation for AUTH_UNIX is broken anyway when
the change would matter but I just don't want it right now). Patch 70
concludes the series, enabling the feature for all other cases. Anything
>70 are bugfixes and trivia.

NFSv4 is unaffected.

Patch summary:
01	sunrpc cleanup, introduction of RPC_MAXGROUPS (16)
26	simplify rpcauth credential code: eliminate bind, unbind and hold operations.
27	comment fixes.
28	proc.c: implement our own rpc_call(), prepare for future rpcauth_lookupcred() calls.
29	nfs3proc.c contains function style macro definitions hiding real functions: rpc_call()
	and rpc_call_sync(). This gets in the ways when the rpc_cred member initialization
	must be moved upwards: 
	-	replace rpc_call() -> nfs3_rpc_call_wrapper() -> nfs3_rpc_wrapper() call tree
		by a call to a new local function named nfs3_rpc() for doing the EJUKEBOX stuff.
	-	replace rpc_call_sync() macro calls by nfs3_rpc() calls
	mailed to Trond.
30	Introduction of rpc_ngroups. move groupinfo stuff down into new unx_add_groups(), the
	cr_add_groups vector in rpc_authops for AUTH_UNIX. Callers of rpcauth_lookupcred() don't
	use the new feature yet so no behavioral change.
40	add rpcauth_lookupcred() calls to nfs2_rpc() and nfs3_rpc(). Disable the new
	feature for all nfsx_rpc() callers for now.
41	nfs_open (open, opendir). We test for the NFS version to avoid any feature leaking
	into the NFSv4 code.
42	nfs_create
43	nfs_lookup/nfs_mkdir/nfs_mknod (touches nfs_symlink via nfs_instantiate)
44	nfs_link
45	nfs_unlink/nfs_rmdir (remove, rmdir). Again a NFS version test to avoid affecting NFSv4
46	nfs_symlink
49	nfs_rename
50	nfs_permission (access) + dfprintk() reporting nfsx_proc_access result.
	Again a NFS version test to avoid affecting NFSv4.
51	nfs_setattr
70	Enable the new code for NFSv2 and NFSv3, adding NULL rpc_groups argument
	to all operations which don't need group info:
		NFSPROC_GETATTR
		NFSPROC_READLINK
		NFSPROC_STATFS
		NFS3PROC_FSINFO
		NFS3PROC_FSSTAT
		NFS3PROC_GETATTR
		NFS3PROC_PATHCONF
		NFS3PROC_READLINK

TODO:
-	The cr_add_groups vector should be folded somehow into the (new in 2.6.12) lookup_cred
	vector. The issue is merely a performance one: do we want 3 extra arguments? could
	it all be avoided by using `current->*' instead?