Draft: Start packaging 4.16.0

This is a first attempt at packaging 4.16.0. I'm creating this MR as a way to discuss this with you, PLEASE DON'T MERGE AS IS.

TODO:

• Integrate the existing patch with orthographic improvements. I'll do it.
• Find a better way to pick the xfceutils library rather than through DEB_LDFLAGS_MAINT_APPEND and DEB_CFLAGS_MAINT_APPEND. I have no idea of how to do it properly, it's too long since I've done some configure.ac magic.