x11: don't wait for asynchronous X resizing with window-scale

Instead of letting the window-scale property return the old value until
X11 actually executed the resize, just set the new assumed internal
window size immediately. This avoids a "lag" between setting and reading
the window-scale property, like OSD controls typically do.

Remove the additional calls from vo_x11_highlevel_resize() - they're
pointless and slightly wrong, and resize events will take care of
updating these things correctly anyway.

Fixes #1176.

("window-scale" works via VOCTRL_[S|G]ET_UNFS_WINDOW_SIZE.)