Add lv_map experimental flag

This is for level-map coefficient coding experiment

Change-Id: Id16c64da3749c91558824f98bdfe4c4982cd03cc

configure

diff --git a/configure b/configure
index f3a706e..eb42b0e 100755
--- a/configure
+++ b/configure
@@ -309,6 +309,7 @@
     tripred
     palette_throughput
     ref_adapt
+    lv_map
 "
 CONFIG_LIST="
     dependency_tracking