Library cleanup not case sensitive

A minor issue, but the library size will increase unnecessarily over time.

Library cleanup is not case sensitive. When a filename is edited, case only, a duplicate entry is created in the library (mp3tag.db3, mtfile table).

e.g., If I change file:
%myfilepath%\1.06 The Beatles - Lucy In The Sky With Diamonds.flac
%myfilepath%\1.06 The Beatles - Lucy in the Sky with Diamonds.flac

Two entries appear in the mtfile table for a single file reference. Cleanup does not resolve/remove the duplicate entry.