x11: fix border toggling

Trying to toggle the border during fullscreen (with "cycle border")
would leave the window stuck without border, and it couldn't be
restored. This was because vo_x11_decoration() always excepted to be
called when toggling the state, and thus confusing the contents of the
olddecor variable. Add got_motif_hints to hopefully prevent this.

Also, when changing the border, don't take fs in account. May break on
older/broken WMs, but all in all is in fact more robust and simpler,
because you do not need to update the border state manually when
returning from fullscreen.
command: disable autorepeat for some commands (actually properties)

Disable autorepeat for the "add"/"cycle" commands when changing
properties that are choices (such as fullscreen, pause, and more).
In these cases, autorepeat is not very useful, and can rather harmful
effects (like triggering too many repeated commands if command
execution is slow).

(Actually, the commands are just dropped _after_ being repeated, since
input.c itself does not know enough about the commands to decide whether
or not they should be repeated.)