[RP] Frame border color

[Göran Gustafsson]

I was just wondering if there are any plans on implementing something like
defbordercolor. I actually thought it was kind of odd when i realised there
was no such thing, i'm not afraid to get my hands dirty and fix it myself but
i plain and simply just can't since i'm not really great when it comes to C.

Anyways, thanks for a great window manager :-)