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

thanks k0ga and stateless for reporting and fixing this issue!

... also some style improvements.

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.

This is the style how it was before the big Xft change. The colors were
inverted, this was not the case before the change.

Reported by "zvz" on #suckless IRC, thanks!

- 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

reproduce: ./dmenu; send EOF; press ctrl+enter.

f6581ca966/monarg.patch becomes upstream now

This allows to run dmenu_path to update the cache using
a packager manager hook system