New reference signaling

This is a new experiment, which removes all the named references and uses ranked
references instead. The last 4 commits are main changes for this experiment, while 
the other 9 commits are cleanups on the baseline.
diff --git a/build/cmake/exports.cmake b/build/cmake/exports.cmake
index fa7842c..e0bfd12 100644
--- a/build/cmake/exports.cmake
+++ b/build/cmake/exports.cmake
@@ -1,12 +1,12 @@
 #
-# Copyright (c) 2017, Alliance for Open Media. All rights reserved
+# Copyright (c) 2021, Alliance for Open Media. All rights reserved
 #
-# This source code is subject to the terms of the BSD 2 Clause License and the
-# Alliance for Open Media Patent License 1.0. If the BSD 2 Clause License was
-# not distributed with this source code in the LICENSE file, you can obtain it
-# at www.aomedia.org/license/software. If the Alliance for Open Media Patent
-# License 1.0 was not distributed with this source code in the PATENTS file, you
-# can obtain it at www.aomedia.org/license/patent.
+# This source code is subject to the terms of the BSD 3-Clause Clear License and
+# the Alliance for Open Media Patent License 1.0. If the BSD 3-Clause Clear
+# License was not distributed with this source code in the LICENSE file, you can
+# obtain it at aomedia.org/license/software-license/bsd-3-c-c/.  If the Alliance
+# for Open Media Patent License 1.0 was not distributed with this source code in
+# the PATENTS file, you can obtain it at aomedia.org/license/patent-license/.
 #
 if(AOM_BUILD_CMAKE_EXPORTS_CMAKE_)
   return()
@@ -27,48 +27,48 @@
 
   set(aom_sym_file "${AOM_CONFIG_DIR}/libaom.${symbol_file_ext}")
 
-  add_custom_target(generate_exports
-                    COMMAND ${CMAKE_COMMAND}
-                            -DAOM_ROOT="${AOM_ROOT}"
-                            -DAOM_CONFIG_DIR="${AOM_CONFIG_DIR}"
-                            -DAOM_TARGET_SYSTEM=${AOM_TARGET_SYSTEM}
-                            -DAOM_SYM_FILE="${aom_sym_file}"
-                            -DAOM_MSVC=${MSVC}
-                            -DAOM_XCODE=${XCODE}
-                            -DCONFIG_NAME=$<CONFIG>
-                            -DCONFIG_AV1_DECODER=${CONFIG_AV1_DECODER}
-                            -DCONFIG_AV1_ENCODER=${CONFIG_AV1_ENCODER}
-                            -DCONFIG_INSPECTION=${CONFIG_INSPECTION}
-                            -DENABLE_TESTS=${ENABLE_TESTS}
-                            -P
-                            "${AOM_ROOT}/build/cmake/generate_exports.cmake"
-                    SOURCES ${AOM_EXPORTS_SOURCES}
-                    DEPENDS ${AOM_EXPORTS_SOURCES})
+  add_custom_target(
+    generate_exports
+    COMMAND
+      ${CMAKE_COMMAND} -DAOM_ROOT="${AOM_ROOT}"
+      -DAOM_CONFIG_DIR="${AOM_CONFIG_DIR}"
+      -DAOM_TARGET_SYSTEM=${AOM_TARGET_SYSTEM} -DAOM_SYM_FILE="${aom_sym_file}"
+      -DAOM_MSVC=${MSVC} -DAOM_XCODE=${XCODE} -DCONFIG_NAME=$<CONFIG>
+      -DCONFIG_AV1_DECODER=${CONFIG_AV1_DECODER}
+      -DCONFIG_AV1_ENCODER=${CONFIG_AV1_ENCODER}
+      -DCONFIG_INSPECTION=${CONFIG_INSPECTION} -DENABLE_TESTS=${ENABLE_TESTS} -P
+      "${AOM_ROOT}/build/cmake/generate_exports.cmake"
+    SOURCES ${AOM_EXPORTS_SOURCES}
+    DEPENDS ${AOM_EXPORTS_SOURCES})
 
   # Make libaom depend on the exports file, and set flags to pick it up when
   # creating the dylib.
   add_dependencies(aom generate_exports)
 
   if(APPLE)
-    set_property(TARGET aom
-                 APPEND_STRING
-                 PROPERTY LINK_FLAGS "-exported_symbols_list ${aom_sym_file}")
+    set_property(
+      TARGET aom
+      APPEND_STRING
+      PROPERTY LINK_FLAGS "-exported_symbols_list ${aom_sym_file}")
   elseif(WIN32)
     if(NOT MSVC)
-      set_property(TARGET aom
-                   APPEND_STRING
-                   PROPERTY LINK_FLAGS "-Wl,--version-script ${aom_sym_file}")
+      set_property(
+        TARGET aom
+        APPEND_STRING
+        PROPERTY LINK_FLAGS "-Wl,--version-script ${aom_sym_file}")
     else()
-      set_property(TARGET aom
-                   APPEND_STRING
-                   PROPERTY LINK_FLAGS "/DEF:${aom_sym_file}")
+      set_property(
+        TARGET aom
+        APPEND_STRING
+        PROPERTY LINK_FLAGS "/DEF:${aom_sym_file}")
     endif()
 
     # TODO(tomfinegan): Sort out the import lib situation and flags for MSVC.
 
   else()
-    set_property(TARGET aom
-                 APPEND_STRING
-                 PROPERTY LINK_FLAGS "-Wl,--version-script,${aom_sym_file}")
+    set_property(
+      TARGET aom
+      APPEND_STRING
+      PROPERTY LINK_FLAGS "-Wl,--version-script,${aom_sym_file}")
   endif()
 endfunction()