This adds a new option in the preferences dialog to show line ending characters only when they differ from what the majority of the line endings in the file use.
So it should be easier to spot accidentally misused line endings.
The idea is from @cousteaulecommandant and shamelessly implemented by me :D.
I guess we can improve the wording of the visible option name and its tooltip.
Screenshot: 
Testfile: [show_differing_eols.zip](https://github.com/geany/geany/files/9542533/show_differing_eols.zip)
You can view, comment on, or merge this pull request online at:
https://github.com/geany/geany/pull/3287
-- Commit Summary --
* Add option to only show line endings if they differ from file default
-- File Changes --
M data/geany.glade (52) M doc/geany.txt (40) M src/editor.c (1) M src/editor.h (1) M src/keyfile.c (2) M src/plugindata.h (2) M src/prefs.c (19) M src/sciwrappers.c (25) M src/sciwrappers.h (1)
-- Patch Links --
https://github.com/geany/geany/pull/3287.patch https://github.com/geany/geany/pull/3287.diff