Use fixed as the default font

dwm's default font in config.h is not guaranteed to be available on all X Window installahttp://sharesource.org/project/fnegronidwm/wiki/font/edit/tions.

Infact, if it is not found, the fixed font will be used instead.

So why not make fixed the default font in the first place?

-static const char font[]            = "-*-terminus-mediumrnormal-*-14-*-*-*-*-*-*-*";
+static const char font[]            = "-misc-fixed-medium-r-semicondensed--13-100-100-100-c-60-iso8859-1";