r23509: This activates the global options from the registry in loadparm.

r23509: This activates the global options from the registry in loadparm.
The global options are stored as values in the subkey "global"
of the SMBCONF registry key.

The activation is accomplished in smb.conf though a new special
semantic of the "include" parameter: "include = registry" triggers
the processing of the registry global options exactly at the
position of the include statement. Options read from the registry
take the same precedence as parameters loaded from a file via
include. Need to reload the registry globals is detected by
watching the tdb sequence number.

Registry shares are automatically activated when the registry
globals are processed.

So a "registry only" configuration can be realized by an
smb.conf that looks as follows:

================================
[global]
include = registry
================================

The global options and registry shares can be conveniently
edited with the "net conf" utility.

Caveat:

A possible pitfall consists in using "include = registry"
together with the "lock directory" directive in the registry.
This problem will be addressed in the next time.

Note on the code:

Processing of the registry options is accomplished by a function
process_registry_globals() in loadparm.c The current version is
only an interim solution: It is handcoded instead of using the
infrastructure of reg_api.c. The reason for this is that using
reg_api still has too large linker dependencies, bloating virtually
all targets by PASSDB_OBJ, SMBLDAP_OBJ, GROUPDB_OBJ and LDB stuff.
A version of process_registry_globals that uses reg_api is
included but commented out. The goal is to eventually refactor
and restructure the registry code so that one can use the reg_api
to access only the registry tdb and not link all the dynamic
backends with all their linking implications.