This makes updating the eyes nicely vblank synchronized.

v2:
	Ensure extensions exist before calling query_version

	These calls add calls to xcb_get_extension_data before calling
	query_version calls, as those calls will mark the connection
	with an error if made against an X server without the
	extension present.

Suggested-by: Uli Schlachter <psychon@znc.in>

v3:
	check the 'present' field in the return from
	xcb_get_extension_data; the xcb_get_extension_data call will
	always succeed (save for out of memory), the only way to tell
	if the extension is supported in the target X server is to
	test the 'present' field in the query extension reply value.

Signed-off-by: Keith Packard <keithp@keithp.com>