Add NCOBMC experimental flag

NCOBMC (non-causal obmc) allows overlapped prediction that takes
mvs from blocks at positions with non-causal relation (e.g. at the
bottom, or to the right) to the current block.
This experiment will be a sub-experiment of MOTION_VAR, so will only
be effective when MOTION_VAR is on.

Change-Id: Ie3aa9591e1c15f5cc251664ea3c146210a5010cf
diff --git a/configure b/configure
index de0f4cb..bf62a8c 100755
--- a/configure
+++ b/configure
@@ -273,6 +273,7 @@
     ext_partition_types
     ext_tile
     motion_var
+    ncobmc
     warped_motion
     entropy
     bitstream_debug