pepper: pepper_plane_t and per-plane damage processing

pepper: pepper_plane_t and per-plane damage processing

Plane is a logical rendering surface maintaing its own damage region. A plane
belongs to an output and a view can be on a plane per output at a time.

<< Overall Data Relationship >>
* Compositor
    - output list
    - view list in sorted z-order

* Output
    - plane list

* Plane
    - plane entry list
    - damage region
    - clip region (obscured by other planes)

* View
    - Geometry (position, size, transform)
    - plane entries

<< Output Repaint Scheduling >>
* surface.commit() causes all outputs to be scheduled to do repaint.
* Repaint is scheduled on an output when one of its plane gets damaged.

<< Output Repaint Process >>
* Update geometry of all views in the compositor.
* Build a list of views that overlap with the output rectangle.
* Ask output backend to assign a plane of each view in the list.
* Build a list of plane entries for the views assigned to each plane.
* Accumulate damage for each plane.
* Call backend.repaint()

<< Damage Processing >>
* Geometry & Z-order change
    - Inflict damage instantly with current visible region of the view on each
      plane where the view belongs to.

    - Mark it as damaged. Damage accumulation function should add visible region
      of damaged views to the planes.

* Plane move
    - Inflict damage instantly on previous plane and mark it as damaged.

* Surface damage
    - Added while accumulating plane damage.

Change-Id: I7c4bd95f439f0cf0356bcbf2f060b09800ea4528