BlackboxWM - 2 New Features & Documentation Cleanup

These patches are mainly just code/documentation cleanup but the split vertical gradient patch and the one that updates the headers should be checked.  The split vertical gradient patch is just one I had archived from back in 2008 when I was using it as my fail-safe window manager (back when Ubuntu was the most popular Linux distribution).  As for the headers, I think I got most of them, but it seems there's still some somewhere as the configure script seems to acquire them again when it's generated.  What I'm not sure about is why GCC doesn't complain about the headers being  deprecated as from what I can tell they have been for a while now.