Set ext_delta_q default and bug fix

* Set ext_delta_q experiment as default
* Update test for ext_delta_q
* Fix a bug (BUG=aomedia:485) in encoder which
  cause decoder and encoder mismatch.

Change-Id: I28ece21c32ff8621f8837ed4807b02eef8c92e29
diff --git a/configure b/configure
index 817085d..5bb32d3 100755
--- a/configure
+++ b/configure
@@ -494,6 +494,7 @@
     soft_enable dual_filter
     soft_enable motion_var
     soft_enable warped_motion
+    soft_enable ext_delta_q
 
     # Backwards/jenkins compatibility with --enable-aom-highbitdepth
     enabled aom_highbitdepth && enable_feature highbitdepth