Enable warped motion on by default

Warped and global motion were adopted in early April.

Change-Id: Ibc619c758224f05244a1f4059e2b506405d46a01
diff --git a/configure b/configure
index 5e105b9..fc844b2 100755
--- a/configure
+++ b/configure
@@ -492,6 +492,7 @@
     soft_enable ext_refs
     soft_enable dual_filter
     soft_enable motion_var
+    soft_enable warped_motion
 
     # Backwards/jenkins compatibility with --enable-aom-highbitdepth
     enabled aom_highbitdepth && enable_feature highbitdepth