Revert "surfaceflinger: Enable dithering if persist.sys.use_dithering=1|2"

This reverts commit f1e55a632098355bf6daea786b20509e7c886ee4.

Conflicts:

	services/surfaceflinger/SurfaceFlinger.cpp
	services/surfaceflinger/SurfaceFlinger.h

Change-Id: I5b7fe8060fc38b581b5717bc1297fdf9dc726c03
Forward-port surface dithering from CM10

This allows the use of 16-bit color displays without excessive color
banding; behavior can be controlled by the persist.sys.use_dithering
property.

Incorporates http://review.cyanogenmod.org/19532 from CM10 as well as
code removed in upstream commit 1b03149.

Change-Id: I290ca4ed4787dc81ac756d9af92cd6a690865a08

Conflicts:

	services/surfaceflinger/SurfaceFlinger.cpp
	services/surfaceflinger/SurfaceFlinger.h