Fixed alpharef.

src/bgfx_shader.sh

@@ -314,7 +314,8 @@ uniform mat4  u_invViewProj;
 uniform mat4  u_model[BGFX_CONFIG_MAX_BONES];
 uniform mat4  u_modelView;
 uniform mat4  u_modelViewProj;
-uniform float u_alphaRef;
+uniform vec4  u_alphaRef4;
+#define u_alphaRef u_alphaRef4.x
 
 #endif // __cplusplus