OpenGL: one more point shader

Added a built-in shader for points that vary both size and color.

source/blender/gpu/shaders/gpu_shader_3D_point_varying_size_varying_color_vert.glsl

@@ -0,0 +1,19 @@
+
+#if __VERSION__ == 120
+  attribute vec3 pos;
+  attribute float size;
+  attribute vec4 color;
+  varying vec4 finalColor;
+#else
+  in vec3 pos;
+  in float size;
+  in vec4 color;
+  out vec4 finalColor;
+#endif
+
+void main()
+{
+	gl_Position = gl_ModelViewProjectionMatrix * vec4(pos, 1.0);
+	gl_PointSize = size;
+	finalColor = color;
+}