Sidebar file sorting issues

[larstobi]

Sorting does not seem work correctly. I expect it to sort alphabetically. Example:

Operating system is Mac OS X Lion
Filesystem is ZFS (MacZFS), case sensitive
MacVim build is from today 10e7bed (branch: split-browser)

[alloy]

This branch is not complete yet. I haven’t had the time to work on it, so patches are very welcome!

[kjyv]

Alphabetical order might or might not have improved (it's fine for me but I'm not on zfs) but in addition, folders should be sorted first, then start with listing files.