Lot of changes here.

1. check_classic_mac_basic.yml — update to latest macOS-latest
2. docker-on-push-tag-or-pr — dependant updates
3. FFTConvolver — fix a compilation warning when the DEBUG flag is turned off
4. Reorganise some source files — e.g. move most of the metadata stuff into a subdirectory
5. Remove unused special-purpose AirPlay 2 RC event handler.
6. Reorganise source files and source code relating to the standard event handler.
7. Check configuration settings a little more carefully to offer more meaningful diagnostics.
8. Add password to AirPlay 2 and reorganise initialisation to set AirPlay 2 flags accordingly.  Also, remove redundant airplay_pin.
9. Remove redundant debug facility definitions from common.h
10. Make it possible to omit all the dacp stuff from a build.
11. Make it possible to omit metadata multicast from a build.
12. Add AP2-native metadata by setting bit 50 of features to true.
13. Improve stability when pre-empting an existing play session.
14. Fix a few compiler warnings in the pair_ap library.
15. Ensure that the audio format is known before starting synchronisation.
16. Improve handle_configure to set/clear a new config setting. Doesn’t seem to do anything…
17. Experimentally turn off bit 46 of AirPlay 2 features — seems to stop failing pair-verify attempts.

.github/workflows/check_classic_mac_basic.yml

@@ -9,9 +9,7 @@ on:
     
 jobs:
   build:
-
-    runs-on: macos-13
-
+    runs-on: macos-latest
     steps:
     - uses: actions/checkout@v6.0.2
     - name: Install Dependencies

.github/workflows/docker-on-push-tag-or-pr.yaml

@@ -59,7 +59,7 @@ jobs:
           fi
       
       - name: Login to Docker Registry
-        uses: docker/login-action@v3.7.0
+        uses: docker/login-action@v4.1.0
         with:
           registry: ${{ secrets.DOCKER_REGISTRY }}
           username: ${{ secrets.DOCKER_REGISTRY_USER }}
@@ -67,13 +67,13 @@ jobs:
         if: needs.docker-vars.outputs.push_docker_image == 'true'
       
       - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3.7.0
+        uses: docker/setup-qemu-action@v4.0.0
       
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v4.0.0
       
       - name: Build and push ${{ matrix.name }}
-        uses: docker/build-push-action@v7.0.0
+        uses: docker/build-push-action@v7.1.0
         env:
           registry_and_name: ${{ secrets.DOCKER_REGISTRY }}/${{ secrets.DOCKER_IMAGE_NAME }}
         with: