Invalidate cached pixmaps on reload and redraw.

After a reload, the drawing parameters for the decorations might
have changed, so we need to invalidate the cache and force a redraw
of the currently visible decorations. Also, don't leak the previous
font when reloading by freeing it before parsing the config.

src/x.c

@@ -307,7 +307,6 @@ void x_draw_decoration(Con *con) {
     p->con_deco_rect = con->deco_rect;
     p->background = config.client.background;
     p->con_is_leaf = con_is_leaf(con);
-    p->font = config.font.id;
 
     if (con->deco_render_params != NULL &&
         (con->window == NULL || !con->window->name_x_changed) &&