Previously the destination dn when restoring an ldap object was
generated in a way that made it really hard to restore do a different
location.
This patch replaces the parser with a much more relaxed approach that
accepts different syntaxes. The new behaviour uses every path component
that contains an equals-sign (=) and builds a DN out of these.

(backport of commit 35451a0)

When the LDAP plugin fails to back up an object, it will be recorded in
the catlog, but the data will be missing.
Previously these objects were silently ignored during restore, leading
to an incomplete set of restored objects.
This patch now adds a rudimentary detection of this case by checking if
plugin_io() is called with IO_READ, IO_WRITE or IO_SEEK between the
calls to IO_OPEN and IO_CLOSE. When there is no call we now emit a
warning that there was no data to restore the object.

(backport of commit e9b60b1)

Previously the plugin would not back up large objects (>64k ldif data).
This patch now adds support for these larger objects.

(backport of commit 7ee398a)

Bareos cannot handle objects with a slash in their name gracefully,
because it is the path delimiter.
This patch adds detection of DNs the contain a slash to the plugin. It
will now correctly raise an error and will no longer try to back up that
data.

(backport of commit 0f53026)

This patch implements compatibility with python-ldap 2.x and 3.x.

(cherry picked from commit c94a0a5)