The sort icon in tabulated-list are opposite of what they should.

This is visible in `package-list-packages` when sorting the "Package" column, when they are alphabetically sorted the icon is like "\/" when it should be like "/\"

I tried to figure out where/how this icon is display, but after a while I got frustrated and thought it'd be easier to ask here.

If you point me to the right place I can do the patch, but as I suspect the fix is trivial it's probably simpler for the one that knows where to look to do the patch.

Thanks,

Philippe