Graphics: Prevent shadow-mapping code to compile without shadow-mapping

Temporary fix for OpenGL 3.3


Former-commit-id: 52d8ae54ee861f85e0cd2c66848c933227d02041 [formerly 3a43b5badc40d76aeca49795ad36d6475510ae68]
Former-commit-id: 39bf34c0ae386859a5bc74106ffccca5adf78475

src/Nazara/Graphics/Resources/Shaders/PhongLighting/core.frag

@@ -94,6 +94,7 @@ float VectorToDepthValue(vec3 vec, float zNear, float zFar)
 	return (normZ + 1.0) * 0.5;
 }
 
+#if SHADOW_MAPPING
 float CalculateDirectionalShadowFactor(int lightIndex)
 {
 	vec4 lightSpacePos = vLightSpacePos[lightIndex];
@@ -119,6 +120,7 @@ float CalculateSpotShadowFactor(int lightIndex)
 	
 	return visibility;
 }
+#endif
 
 void main()
 {