Add NEW_MULTISYMBOL experiment.

This experiment is for converting binary symbols in the baseline
into non-binary symbols. EC_MULTISYMBOL should continue to be used
by experiments with their own signalling for compatibility.

Change-Id: Idc11a469b1806948107c0d6966235f3053c43519

configure

@@ -313,6 +313,7 @@ EXPERIMENT_LIST="
     lv_map
     mv_compress
     frame_superres
+    new_multisymbol
 "
 CONFIG_LIST="
     dependency_tracking
@@ -489,6 +490,7 @@ post_process_cmdline() {
     enabled pvq && enable_feature ec_adapt
     enabled ec_adapt && enable_feature ec_multisymbol
     enabled new_tokenset && enable_feature ec_multisymbol
+    enabled new_multisymbol && enable_feature ec_multisymbol
     enabled ec_multisymbol && ! enabled ans && soft_enable daala_ec
     enabled ec_multisymbol && ! enabled daala_ec && soft_enable ans
     enabled palette_throughput && soft_enable palette