this fixes a crash on NetBSD because it requires -D_XOPEN_SOURCE (strdup, usleep).

thanks k0ga and stateless for reporting and fixing this issue!

These variables make it simpler to change the paths to this for ports.
`pkg-config` is avoided because it sucks, in particular for cross-compilation.

A commented path for *BSD is added, the Xft includes are located at:
/usr/X11R6/include there.

Also already bump the version number to 4.6, a release will come
approximately in August.

- 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