weekend work. user / group database API.

- split sam_passwd and smb_passwd into separate higher-order function tables

- renamed struct smb_passwd's "smb_user" to "unix_user".  added "nt_user"
plus user_rid, and added a "wrap" function in both sam_passwd and smb_passwd
password databases to fill in the blank entries that are not obtained
from whatever password database API instance is being used.

NOTE: whenever a struct smb_passwd or struct sam_passwd is used, it MUST
be initialised with pwdb_sam_init() or pwd_smb_init(), see chgpasswd.c
for the only example outside of the password database APIs i could find.

- added query_useraliases code to rpcclient.

- dealt with some nasty interdependencies involving non-smbd programs
and the password database API.  this is still not satisfactorily
resolved completelely, but it's the best i can do for now.

- #ifdef'd out some password database options so that people don't
mistakenly set them unless they recompile to _use_ those options.

lots of debugging done, it's still not finished.  the unix/NT uid/gid
and user-rid/group-rid issues are better, but not perfect.  the "BUILTIN"
domain is still missing: users cannot be added to "BUILTIN" groups yet,
as we only have an "alias" db API and a "group" db API but not "builtin-alias"
db API...

source/rpc_client/cli_lsarpc.c

@@ -309,7 +309,7 @@ BOOL do_lsa_lookup_sids(struct cli_state *cli,
 					fstrcpy(dom_name, unistr2(ref.ref_dom[dom_idx].uni_dom_name.buffer));
 					fstrcpy(name    , unistr2(t_names.uni_name[i].buffer));
 					
-					slprintf(full_name, sizeof(full_name), "\\%s\\%s",
+					slprintf(full_name, sizeof(full_name), "%s\\%s",
 						 dom_name, name);
 
 					(*names)[i] = strdup(full_name);