docs: Add missing ARB_gpu_shader5 subfeature to GL3.txt

Signed-off-by: Chris Forbes <chrisf@ijw.co.nz>
diff --git a/docs/GL3.txt b/docs/GL3.txt
index cebb099..273f9b7 100644
--- a/docs/GL3.txt
+++ b/docs/GL3.txt
@@ -112,6 +112,7 @@
   - Geometry shader multiple streams                   not started
   - Enhanced per-sample shading                        DONE
   - Interpolation functions                            started
+  - New overload resolution rules                      not started
   GL_ARB_gpu_shader_fp64                               not started
   GL_ARB_sample_shading                                DONE (i965, nv50, nvc0)
   GL_ARB_shader_subroutine                             not started