[PATCH] AD: Add initial gpo-smb implementation.

[Yassir Elley]

Hi,

The attached patch adds an initial gpo-smb implementation. It uses SMB to retrieve HBAC
policy files, evaluate them, and enforce the whitelists and blacklists found in those
policy files. This is an initial implementation and there are a few things that I am
planning on implementing, but are not part of this patch.

This patch does not implement:
* the "permissive" mode, in which the policy files are evaluated, but not
enforced
* a separate gpo_child process to make the blocking libsmbclient calls
* use of a cache
* few other things

As such, most of this patch will be moved to a separate gpo_child process in a subsequent
patch.

Also note that some (but not all) of the changes that were pushed to master as part of my
patch titled "add libsmbclient to makefiles" seem to have been deleted by
subsequent pushes to master. As such, this patch reintroduces those changes (which only
affect configure.ac and libsmbclient.m4).

Regards,
Yassir.