Consider motif border for floating geometry

Long description:

When calculating the geometry of a floating window with motif hints that
specify a border style, take into account that this window will have a
different border style when calculating its position with
floating_enable() when the window becomes managed.

A nice side effect of this is that users can override motif hints with
`new_float` config directives when they are specified other than
`normal`.

fixes #1270

To apply this patch, use:
curl http://cr.i3wm.org/patch/598/raw.patch | git am

@@ -436,11 +436,6 @@ void manage_window(xcb_window_t window, xcb_get_window_attributes_cookie_t cooki

     if (nc->geometry.width == 0)

         nc->geometry = (Rect) {geom->x, geom->y, geom->width, geom->height};

-    if (want_floating) {

-        DLOG("geometry = %d x %d\n", nc->geometry.width, nc->geometry.height);

-        floating_enable(nc, true);

-    }

-

     if (motif_border_style != BS_NORMAL) {

         DLOG("MOTIF_WM_HINTS specifies decorations (border_style = %d)\n", motif_border_style);

         if (want_floating) {

@@ -450,6 +445,16 @@ void manage_window(xcb_window_t window, xcb_get_window_attributes_cookie_t cooki

         }

     }

+    if (want_floating) {

+        DLOG("geometry = %d x %d\n", nc->geometry.width, nc->geometry.height);

+        /* motif hints will be applied only when `new_float` is `normal` or not

+         * specified */

+        bool automatic_border = (config.default_floating_border != BS_NORMAL &&

+                motif_border_style == BS_NORMAL);

+

+        floating_enable(nc, automatic_border);

+    }

+

     /* to avoid getting an UnmapNotify event due to reparenting, we temporarily

      * declare no interest in any state change event of this window */

     values[0] = XCB_NONE;