I don't know since when this was introduced but I see the atlas generated by ttf files to be wrong.

On the latest master opengl_example as reference

//Default font should be proggyclean at 13
 io.Fonts->AddFontDefault()

io.Fonts->AddFontFromFileTTF("../../extra_fonts/ProggyClean.ttf", 13.0f);

Am I missing something that has changed in font handling with oversampling or is this a bug?