Kill RID-only and domain+RID madness from winbind.

Kill RID-only and domain+RID madness from winbind.

Now we deal with SIDs in almost all of winbind (a couple of limited exceptions
remain, but I'm looking into them - they use non-winbind structs ATM).

This has particular benifits in returning out-of-domain SIDs for group
membership (Need to look into this a bit more) as well as general code quality.

This also removes much of the complexity from the idmap interface, which now
only deals with mapping IDs, not with SID->domain translations.

Breifly tested, but needs more.  Fixes some valgrind-found bugs from my
previous commit.

Winbind cache chagned to using SID strings in some places, as I could not
follow exactly how to save and restore multiple packed sids properly.

Andrew Bartlett
(This used to be commit 9247cf08c40f016a924d600ac906cfc6a7016777)