r4885: added a new NBT client library. Features include:

r4885: added a new NBT client library. Features include:

 - structures defined using IDL in nbt.idl
 - build around our events structure, and talloc
 - fully async
 - supports all NBT packet fields as per rfc1002
 - easy interfaces for name query and status

For the moment there are just a couple of test functions in
namequery.c, test_name_query() and test_name_status(). These will be
removed when we hook the new library into libcli/ fully

The new library will also be a fairly good basis for a nbt
server. Although it can't be a server as-is, I wrote it with the needs
of a server in mind (for example, extremely scalable idtree based
packet handling)