x11_common: fix for reconfig with pos/xineramascreen set

x11_common: fix for reconfig with pos/xineramascreen set

vo_x11_create_vo_window() only called vo_x11_update_geometry() if no
window position had been specified by -geometry or -xineramascreen, to
avoid overwriting the specified position with values from the existing
window. However window size should be initialized to the existing
window here, and setting new window title for -use-filename-title is
also done in vo_x11_update_geometry() (for whatever reason, it doesn't
match what else that function does). Change the code in
vo_x11_create_vo_window() to always call vo_x11_update_geometry() for
size variable and window title updates, but add a flag that tells it
not to update position variables.