Use libdraw: add Xft and fallback-fonts support to graphics lib

- libdraw, util: add drw.{c,h}, util.{c,h} and update code.
- libdraw: fix drw_rect(): use w and h parameter.
- libdraw: print errstr if last character in string was ":" (sbase).
- libdraw: drw_clr_free() allow valid free(NULL).
- config.def.h: set default font to monospace.
- cleanup() on exit.
- LICENSE: update license string for dmenu -v to 2015.
- LICENSE: add myself to LICENSE

LICENSE

@@ -7,6 +7,7 @@ MIT/X Consortium License
 © 2009 Evan Gates <evan.gates@gmail.com>
 © 2006-2008 Sander van Dijk <a dot h dot vandijk at gmail dot com>
 © 2006-2007 Michał Janeczek <janeczek at gmail dot com>
+© 2014-2015 Hiltjo Posthuma <hiltjo@codemadness.org>
 
 Permission is hereby granted, free of charge, to any person obtaining a
 copy of this software and associated documentation files (the "Software"),