permission: Fix hiding the border for maximized clients.

When the theme variables were moved to the backend instead of `rc.lua`,
some magic was added to disable them if the user set the border. However,
some undocumented `awful.placement` code also set them and turned off
the theme variables. So it worked *once* then stopped working.

lib/awful/permissions/init.lua

@@ -631,10 +631,16 @@ function permissions.update_border(c, context)
     end
 
     if not c._private._user_border_width then
-        c._border_width = beautiful["border_width"..suffix]
+        local bw = beautiful["border_width"..suffix]
             or beautiful["border_width"..fallback1]
             or beautiful["border_width"..fallback2]
-            or beautiful.border_width
+
+        -- The default `awful.permissions.geometry` handler removes the border.
+        if (not bw) and (c.fullscreen or c.maximized) then
+            bw = 0
+        end
+
+        c._border_width = bw or beautiful.border_width
     end
 
     if not c._private._user_border_color then

lib/awful/placement.lua

@@ -383,7 +383,7 @@ end
 area_common = function(d, new_geo, ignore_border_width, args)
     -- The C side expect no arguments, nil isn't valid
     if new_geo and args.zap_border_width then
-        d.border_width = 0
+        d._border_width = 0
     end
     local geometry = new_geo and d:geometry(new_geo) or d:geometry()
     local border = ignore_border_width and 0 or d.border_width or 0
@@ -1633,7 +1633,7 @@ function placement.restore(d, args)
 
     end
 
-    d.border_width = memento.border_width
+    d._border_width = memento.border_width
 
     -- Don't use the memento as it would be "destructive", since `x`, `y`
     -- and `screen` have to be modified.