weston: fix boolean wayland backend options

weston: fix boolean wayland backend options

Surprisingly, WESTON_OPTION_BOOLEAN uses the type int32_t, not bool.
Passing in a pointer bool does not end well. Fix this to pass in
pointers as parse_options() expects.

This fixes a bug where 'weston --use-pixman --sprawl' would work but
'weston --sprawl --use-pixman' would ignore the --sprawl option.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Acked-by: Daniel Stone <daniels@collabora.com>