Handle entropy coder experiment dependencies

Change-Id: I854c53d9379f820b5a78fcb53f9ef09bc6f9d9e7
diff --git a/configure b/configure
index 292f0e6..21fde7a 100755
--- a/configure
+++ b/configure
@@ -454,6 +454,10 @@
         enabled ${c} && enable_feature ${c##*_}s
     done
 
+    # Fix up experiment dependencies
+    enabled ec_adapt && ! enabled rans && soft_enable daala_ec
+    enabled ec_adapt && ! enabled daala_ec && soft_enable rans
+    enabled rans && enable_feature ans
     if enabled global_motion && (enabled ext_inter || enabled dual_filter); then
       log_echo "global_motion currently not compatible with ext_inter"
       log_echo "and dual_filter. Disabling global_motion."