Preparation of release 1.4.5

[Albrecht Schlosser]

I am in the process of preparing the next public release 1.4.5, but
there is still something to do before we can release it. There is no
schedule yet but I hope we can release 1.4.5 by the end of February
(2026 ;-) ).

For now I updated the version number(s) in all relevant files with the
goal to check ABI compatibility. So far I didn't find any issues.

I created a new milestone "FLTK 1.4.5" on GitHub:
https://github.com/fltk/fltk/milestone/11

Please add issues that *must* be fixed in 1.4.5 to this milestone, but
keep in mind that only severe bugs should be fixed, and that no new
features should be added to 1.4.x releases. Note that we have already 36
commits since release 1.4.4.

Please add a comment to this thread if you think anything else is worth
(necessary) considering for 1.4.5.