Move libnet_conf to a library lib/smbconf/ of its own, fixing the api.

Move libnet_conf to a library lib/smbconf/ of its own, fixing the api.

The libnet_conf code to access the registry based configuration has
become more of a library used in several places in samba (e.g. loadparm)
than an abstraction of "net conf". So I move it to a location lib/smbconf/.

In the same breath, the api is fixed (not generated by make proto anymore).

Michael
(This used to be commit 5315ef41f403b96715dd68b512e9e74662e2910a)