Changes: - authproto_pam: all pam_setcred. - main: detect current Xss state at startup. - main: wakeup on SIGUSR2. - saver_mpv: perform playlist looping inside mpv. - saver_multiplex: export screen saver index as XSCREENSAVER_SAVER_INDEX to sub-savers. - XSECURELOCK_MULTIPLEX_BACKGROUND_COLOR: configurable background color. - XSECURELOCK_SAVER_DELAY_MS: allow sleeping before mapping windows, for smoother initialization of children. - XSECURELOCK_VIDEOS_FLAGS: flags for mpv (and also mplayer).