Re-introduced alphaDiscardThreshold in lighting frag

git-svn-id: https://jmonkeyengine.googlecode.com/svn/trunk@9768 75d07b2b-3a1a-0410-a2c5-0572b91ccdca

engine/src/core-data/Common/MatDefs/Light/Lighting.frag

@@ -55,6 +55,8 @@ varying vec3 SpecularSum;
   uniform sampler2D m_ColorRamp;
 #endif
 
+uniform float m_AlphaDiscardThreshold;
+
 #ifndef VERTEX_LIGHTING
 uniform float m_Shininess;
 
@@ -170,6 +172,9 @@ void main(){
     #ifdef ALPHAMAP
        alpha = alpha * texture2D(m_AlphaMap, newTexCoord).r;
     #endif
+    if(alpha < m_AlphaDiscardThreshold){
+        discard;
+    }
 
     #ifndef VERTEX_LIGHTING
         float spotFallOff = 1.0;