Add first cut at a shader based chroma key facility 1. Added a new CHROMA <GREEN|BLUE> [alpha blend start, alpha blend stop] command. 2. Added a glsl shader and integrated into the existing pixel shader.

Signed-off-by: cambell <cambell_prince@sil.org>
Signed-off-by: cambell <cambell.prince@gmail.com>
Use glsl clamp function and remove the last explict conditionals from the chroma shader

Signed-off-by: cambell <cambell_prince@sil.org>
Signed-off-by: cambell <cambell.prince@gmail.com>
wip chroma

Signed-off-by: cambell <cambell.prince@gmail.com>
wip chroma shader, and command

Signed-off-by: cambell <cambell.prince@gmail.com>
wip chroma

Signed-off-by: cambell <cambell.prince@gmail.com>
wip spill suppression

Signed-off-by: cambell <cambell.prince@gmail.com>
chroma: blend in alpha rather than 1.0.

Signed-off-by: cambell <cambell.prince@gmail.com>
Rewrite spill supression to accept a user setable threshold value

Also switch to smooth interpolation and adjust alpha too

Signed-off-by: cambell <cambell_prince@sil.org>
Signed-off-by: cambell <cambell.prince@gmail.com>
Alter MIXER BLEND command to take chroma threshold + spread rather than start stop

Signed-off-by: cambell <cambell_prince@sil.org>
Signed-off-by: cambell <cambell.prince@gmail.com>
chroma: Fix shader

Signed-off-by: cambell <cambell.prince@gmail.com>
Separate out the chroma key parameters from BLEND into separate MIXER command

Signed-off-by: cambell <cambell_prince@sil.org>
Signed-off-by: cambell <cambell.prince@gmail.com>
Fix FTBFS bugs

Signed-off-by: cambell <cambell.prince@gmail.com>
Merge branch 'chroma-wip' into build-cp