Add ref-mv experiment flag

Change-Id: Ie2101e362aeb01681313adf67596bc6b479e873e
diff --git a/configure b/configure
index 315c427..27d618b 100755
--- a/configure
+++ b/configure
@@ -267,6 +267,7 @@
     fp_mb_stats
     emulate_hardware
     var_tx
+    ref_mv
     ext_tx
     misc_fixes
     ext_intra