Log Message:
PR pkg/41731: maintainer update of wm/dwm to dwm-5.6.

Changes:
 o new Xinerama support that creates a view per Xinerama screen.
   Focusing different screens works using the mouse or
   the new shortcuts Mod1-. and Mod1-, (or Mod1-Shift-, and Mod1-Shift-.
   for sending windows to next/prev screen).
 o Extended Rule structure in config.h with an additional monitor field
   (-1 if a client should be assigned to the selected screen, or 0.. for a
   specific screen)
 o Several bugfixes in the resize handling