- extract drawitem function (code deduplication)
- fix bug where inputw was not correctly calculated from the widest item, but
  just from the one with the longest strlen() which is not the same. It's better
  now, but does not account for fallback fonts, since it would be too slow to
  calculate all the correct item widths on startup.
- minor code style fixes (indentation, useless line breaks)

... we don't allow passing text is NULL anymore either, for that behaviour
just use drw_rect() (it is used in dwm).

don't do these checks on this level. However for resource drw_*_free
we will allow it.

... remove intermediary variables

this makes the code-style more consistent aswell.

- 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