r21884: * Blacklist BUILTIN and MACHINE domains from the
idmap domains as these should only be handled by the
winbindd_passdb.c backend
* Allow the alloc init to fail for backwards compatible
configurations like
idmap backend = ad
idmap uid = 1000-100000
....
* Remove the deprecated flags from idmap backend, et. al.
These are mutually exclusive with the new configuration
options (idmap domains). Logging annoying messages
about deprecated parameters is confusing. So we'll try
this apprpach for now.