RFC: Preparation of release 1.4.4

[Albrecht Schlosser]

Dear FLTK devs,

please take a look at GitHub Issue #1281 and add your comments
https://github.com/fltk/fltk/issues/1281

I used a GitHub Issue because it provides direct links to the commits I
wanted to refer to, and it also supports check marks when items are
done. I added the above mentioned issue to milestone "FLTK 1.4.4".

Thanks in advance