This update for lightdm fixes the following issues:

- Fixed issue with glibc 2.33 (boo#1181778).
- Only build the qt4 subpackage up to Leap 15.2 / SLE 15 SP2
(boo#1179613)
- Change paths from /etc to /usr/etc for UsrEtc Move (boo#1177197)

- Fixup pam stack a bit more (boo#1176338):
+ Do not create hardlinks between lightdm pam files and xdm's pam
files, but install explicit lightdm pam stack that @includes
xdm. This has the advantage that, if an admin creates
/etc/pam.d/xdm, we will follow this right away. With the
hardlinks, the /usr/etc/pam.d/xdm would still be used, which
might not be the expected outcome.

- Follow XDM's change of moving the default pam config file to
/usr/etc (boo#1176338).
- Add pre/posttrans scripts to ensure user modified
/etc/pam.d/lightdm* survives our move to /usr/etc (and user
modification in /etc/pam.d wins over /usr/etc/pam.d).

- Fixes for %_libexecdir changing to /usr/libexec

Update to version 1.30.0:

* Add lightdm_user_get_is_locked ().
* Hide users with shell /bin/false.
* Remove unity-system-compositor support (dead upstream).
* Fix dm-tool crash.
* Update documentation.

Update to version 1.28.0:

* Continue to shutdown session if removing X authority fails.
* Set XDG_SEAT env variable in script hooks.
* Fix small leak in XDMCP server.
* liblightdm-qt: Mark class PowerInterface as exported.
* Fix one qt5 test being run instead of a qt4 one.
* Remove use of deprecated g_type_class_add_private.
* Modernise private data in objects.
* Document XDG_SEAT_PATH in man page.
* Fix install failing if link already exists.

Update to version 1.26.0:

* Fix build system to require C99.
* Support moc being called moc-qt5.
* Fail configure if MOC can't be found.
* Use AccountsService extension system for extended greeter
information.
* Fix incorrect use of ConsoleKit CanSuspend/Hibernate API.
* Use standard format for arguments passed to qtchooser.
* Modernise code style.