Description of the Issue

Line sorting is not ordering related letters correctly when there are diacritics (such as "e", "è" and "ë")

Steps to Reproduce the Issue

See the related community post:
https://community.notepad-plus-plus.org/topic/19613/does-sort-lines-lexographically-have-a-bug-with-diacritics

Here's a list:
naval
neither
nèither
never
nëver
nothing

Select all, then Edit > Line Operations > Sort Lines Lexographically Ascending. The list is changed to:
naval
neither
never
nothing
nèither
nëver

This is not correct because users of languages using diacritics would expect the order of letters to be:
…deèéêëf…

rather than:
…def…èéêë…

Expected Behavior

List is already sorted, so not change

Actual Behavior

List was changed to:
naval
neither
never
nothing
nèither
nëver

Debug Information

Notepad++ v7.8.6 (64-bit)
Build time : Apr 21 2020 - 15:23:03
Path : C:\Program Files\Notepad++\notepad++.exe
Admin mode : OFF
Local Conf mode : OFF
OS Name : Windows 10 Pro (64-bit)
OS Version : 1903
OS Build : 18362.900
Plugins : CustomizeToolbar.dll DSpellCheck.dll mimeTools.dll NppConverter.dll NppExport.dll PythonScript.dll