NORSPEC-280 include fix to downsampleDepthRect shader making GL 3.3. drivers cry

indra/newview/app_settings/shaders/class1/interface/downsampleDepthRectF.glsl

@@ -23,6 +23,8 @@
  * $/LicenseInfo$
  */
 
+#extension GL_ARB_texture_rectangle : enable
+
 #ifdef DEFINE_GL_FRAGCOLOR
 out vec4 frag_color;
 #else