Initial pass at SurfaceFlinger effects, night mode.

This change adds a mRenderEffect variable that can be used
to control rendering effects at runtime.  One example effect
of "night mode" is included which renders the entire system
in using a red-only filter.

In particular, this is useful on devices with OLED displays
where the power consumption of the red channel is much less
than green and blue.

Change-Id: I64fb47a186e5b1c6be5db7e179ab6796e66bf341