Fix bubble shader with glsl < 330.

data/shaders/bubble.vert

@@ -21,8 +21,13 @@
 uniform mat4 ModelViewProjectionMatrix;
 uniform float time;
 
+#if __VERSION__ >= 330
 layout(location = 0) in vec3 Position;
 layout(location = 3) in vec2 Texcoord;
+#else
+in vec3 Position;
+in vec2 Texcoord;
+#endif
 out vec2 uv;
 
 void main()