Removed AdditiveAlphaBlending constant. Fixes #2146.

src/materials/Material.js

@@ -58,8 +58,7 @@ THREE.NormalBlending = 1;
 THREE.AdditiveBlending = 2;
 THREE.SubtractiveBlending = 3;
 THREE.MultiplyBlending = 4;
-THREE.AdditiveAlphaBlending = 5;
-THREE.CustomBlending = 6;
+THREE.CustomBlending = 5;
 
 // custom blending equations
 // (numbers start from 100 not to clash with other