Colorout (xform codepath): speedup

Use TYPE_LabA_FLT and TYPE_RGBA_FLT, thus removing need for intermediate buffer, and adding support for usage of SSE2 intrinsics

Speed gain (on export, not 100% correct): 
186 "timer ticks" (no gamutcheck) -> 56 (or 6? (with gamutcheck)), 6 (or 0??? (no gamutcheck))