compositor: Switch to new surface/view mapped checks

This patch makes use of new flags which were introduced
by previous patches to check if a surface/view is mapped

v2:

- Rebased to apply on git master
- Added comments with link to discussion about proposed
  changes for weston_{surface,view}_is_mapped()

Signed-off-by: Armin Krezović <krezovic.armin@gmail.com>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
1 file changed