lib/fs: Add case insensitivity to MtimeFS

Browse Source

This is step one of a hundred fifty on the path to case insensitivity.
It brings in the basic case folding mechanism and adds it to the
mtimefs, as this is something outside the fileset that touches stuff in
the database based on name. No effort to convert or handle existing
entries when the insensitivity is changed, I don't think we need it...

Useless by itself but includes tests and will reduce the review load
along the way.

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4521

...

This commit is contained in:

500 Internal Server Error

Gitea Version: 1.28.0+dev-477-g8b6ad49a5f