Regular expression switches don't recognize non-latin text

Npp regex switched don't work on non-latin texts it.

Description of the Issue

I'm trying to change character case in some cyrillic texts using Find&Replace and regular expressions. Unfortunatelly Npp understands \L\l\U\u switches only on latin characters. All other unicode characters are ignored, and there is not way to tell Npp how to handle them properly.

Steps to Reproduce the Issue

1. Type some non-latin text in upper-case (i.e. ФЫВА ОЛДЖ)
2. Open Replace dialog (Ctrl+H)
3. Find what: (\w+)
4. Replace with: \L$1
5. Select "Regular expressions" option.
6. Click "Replace All"

Expected Behavior

Text to be replaced with lower-case version (i.e. фыва олдж)

Actual Behavior

Text remains upper-case (i.e. ФЫВА ОЛДЖ)

Debug Information

Notepad++ v7.3 (32-bit)
Build time : Jan 1 2017 - 20:04:42
Path : C:\Notepad++\notepad++.exe
Admin mode : OFF
Local Conf mode : ON
OS : Windows 10
Plugins : mimeTools.dll NppConverter.dll NppExport.dll NppSharp.dll PluginManager.dll

Reproduce the issue through the Find & Replace dialog using the listed Cyrillic text, regular-expression mode, and the replacement \L$1. Trace the regular-expression replacement handling and verify that Replace All converts non-Latin Unicode characters to lowercase while preserving the existing Latin behavior.