[dwm] simplified config.*.h handling

I removed the config.h creation from config.default.h now. The
both shipped config.h's only differed in appearance definitions
I will revert the fallback to fixed font if a specific font
is not installed again that those things work smoothly - since
the terminus font was/is the only reason I hesitated this change
for quite a long period.

Regards,

-- 
 Anselm R. Garbe >< http://www.suckless.org/ >< GPG key: 0D73F361