FreeIPA ID views allow to override POSIX attributes for certain
users and groups.

A support is added to allow using specific ID view when serving
compatibility tree. Each user or group entry which has an override
in the view is amended with the overridden values from the view
before served out to the LDAP client.

A view to use is specified as a part of base DN:

	cn=<view>,cn=views,cn=compat,$SUFFIX

where cn=compat,$SUFFIX is the original compatibility tree base DN.

Each entry, when served through the view, gets new DN rewritten to
specify the view. Additionally, if override in the view changes
uid (for users) or cn (for groups) attribute, the entry's RDN is changed
accordingly.

For groups memberUid attribute is modified as well in case there is an override
in the view that changes uid value of that member.

FreeIPA ID views support overrides for users of trusted Active Directory domains.
In case of a trusted AD domain's user or group is returned via compatibility tree,
view overrides are applied in two stages:
  1. SSSD applies default view for AD users
  2. slapi-nis applies explicitly specified (host-specific) view
     on top of the entry returned by SSSD

Thus, slapi-nis does not need to apply default view for AD users and if there are
no host-specific views in use, there is no need to specify a view in the base DN,
making overhead of a default view for AD users lower.

The values for NIS hosts.byname and hosts.byaddr maps should start with
addresses, not names.  Reported by Rik Megens.

Avoid calling strdup() in a situation where we don't need to, so that we
can better handle cases where it fails (static analysis).

Treat "schema-compat-lookup-nsswitch: passwd" in the configuration the
same as "schema-compat-lookup-nsswitch: user", to not fail for people
who forget and try to use the nsswitch database name.

If we hit out-of-memory (strdup() failures) while reading the
configuration, don't crash (static analysis).  In some cases,
this means we proceed with garbage data until the copy_config()
function sanity-checks its input and output.

If we hit out-of-memory (strdup() failures) while reading the
configuration, don't crash (static analysis).