Destroying the first back buffer before the other ones might cause an already
freed surface to be used as target in FindContext().

It was computing the number of submenus in the branch, rather then the
maximum depth.

C++ doesn't like: GUID GUID; which is valid in C, so replace with
struct _GUID GUID;

secur32: Revert "secur32: Work around ntlm_auth in Samba 3.0.28a being broken for cached credentials".

This reverts commit 7788c8ed, as well
as commit ec443be7. Due to erroneous
user input, these commits actually broke more than they fixed.

This fixes a regression introduced by fb77678e.