[Cin] new overlay mode from Freelancer

finally looked at history.. http://git.cinelerra-gg.org/git/?p=goodguy/history.git;a=blobdiff;f=cinelerr... and made this patch (attached) it works softer than logical or porter/duff modes, but notiecably slower ( (on 8 core arm tablet) my modes fails to compile - something about me not really knowing how to write macro functions (?)