wm/blackbox70: update to version 0.74

While here, add a LICENSE definition, and fix compliation on some Linux
distributions.

Change log:

Release blackbox-0.74 released 2018-10-31
-----------------------------------------

Brian Bidulock <bidulock@openss7.org> (9):
      update po files
      add a release file
      remove bashisms from gennews.sh
      make autogen.sh handle gnits and remove bashisms
      5-part AC_INIT and prefer asciidoc to asciidoctor
      generate and distribute release file
      add release files to .gitignore
      update po files
      update release files

Brian Bidulock <bidulock@openss7.com> (1):
      Merge pull request #19 from vl-80/fullscreen_fix

VL-80 <vl-80@users.noreply.github.com> (1):
      Fix fullscreen mode for non-maximized windows

Release blackbox-0.73 released 2018-05-28
-----------------------------------------

Brian Bidulock <bidulock@openss7.org> (18):
      zero errno when not using it
      silent rules with /usr prefix
      add branch to substitution
      add more checks
      update make flags
      silent now default
      tweaks
      add some ignores
      better build
      update install file
      initialize XKEYBOARD
      update po files
      become child subreaper and session leader
      Merge branch 'master' of github.com:bbidulock/blackboxwm
      prctl is linux-specific
      update po files
      update release files
      update release files

Brian Bidulock <bidulock@openss7.com> (1):
      Merge pull request #13 from psolyca/master

Damien Gaignon <damien.gaignon@gmail.com> (1):
      Add errno.h as include


(gutteridge)