CONTRIB: move src/wurfl.c and contrib/wurfl to addons/wurfl

Both the source file and the dummy library are now at the same place.
Maybe the build howto could be moved there as well to make things even
cleaner.

The Makefile, MAINTAINERS, doc, and vtest matrix were updated.
diff --git a/.github/matrix.py b/.github/matrix.py
index 4db8767..22c33f0 100644
--- a/.github/matrix.py
+++ b/.github/matrix.py
@@ -77,8 +77,8 @@
                 "USE_OPENSSL=1",
                 "USE_SYSTEMD=1",
                 "USE_WURFL=1",
-                "WURFL_INC=contrib/wurfl",
-                "WURFL_LIB=contrib/wurfl",
+                "WURFL_INC=addons/wurfl/dummy",
+                "WURFL_LIB=addons/wurfl/dummy",
                 "USE_DEVICEATLAS=1",
                 "DEVICEATLAS_SRC=addons/deviceatlas/dummy",
                 "USE_PROMEX=1",
@@ -143,8 +143,8 @@
             "USE_OPENSSL=1",
             "USE_SYSTEMD=1",
             "USE_WURFL=1",
-            "WURFL_INC=contrib/wurfl",
-            "WURFL_LIB=contrib/wurfl",
+            "WURFL_INC=addons/wurfl/dummy",
+            "WURFL_LIB=addons/wurfl/dummy",
             "USE_DEVICEATLAS=1",
             "DEVICEATLAS_SRC=addons/deviceatlas/dummy",
             "USE_PROMEX=1",
diff --git a/.github/workflows/coverity.yml b/.github/workflows/coverity.yml
index 12d08e6..fd5a0e2 100644
--- a/.github/workflows/coverity.yml
+++ b/.github/workflows/coverity.yml
@@ -17,7 +17,7 @@
       COVERITY_SCAN_PROJECT_NAME: 'Haproxy'
       COVERITY_SCAN_BRANCH_PATTERN: '*'
       COVERITY_SCAN_NOTIFICATION_EMAIL: 'chipitsine@gmail.com'
-      COVERITY_SCAN_BUILD_COMMAND: "make CC=clang TARGET=linux-glibc USE_ZLIB=1 USE_PCRE=1 USE_PCRE_JIT=1 USE_LUA=1 USE_OPENSSL=1 USE_SYSTEMD=1 USE_WURFL=1 WURFL_INC=contrib/wurfl WURFL_LIB=contrib/wurfl USE_DEVICEATLAS=1 DEVICEATLAS_SRC=addons/deviceatlas/dummy USE_51DEGREES=1 51DEGREES_SRC=addons/51degrees/dummy/pattern"
+      COVERITY_SCAN_BUILD_COMMAND: "make CC=clang TARGET=linux-glibc USE_ZLIB=1 USE_PCRE=1 USE_PCRE_JIT=1 USE_LUA=1 USE_OPENSSL=1 USE_SYSTEMD=1 USE_WURFL=1 WURFL_INC=addons/wurfl/dummy WURFL_LIB=addons/wurfl/dummy USE_DEVICEATLAS=1 DEVICEATLAS_SRC=addons/deviceatlas/dummy USE_51DEGREES=1 51DEGREES_SRC=addons/51degrees/dummy/pattern"
     steps:
     - uses: actions/checkout@v2
     - name: Install apt dependencies
@@ -33,7 +33,7 @@
         # quoting into account.
         sed -i 's/^DEBUG =$/DEBUG = -DDEBUG_STRICT=1 -DDEBUG_USE_ABORT=1/' Makefile
     - name: Build WURFL
-      run: make -C contrib/wurfl
+      run: make -C addons/wurfl/dummy
     - name: Run Coverity Scan
       env:
         COVERITY_SCAN_TOKEN: ${{ secrets.COVERITY_SCAN_TOKEN }}
diff --git a/.github/workflows/vtest.yml b/.github/workflows/vtest.yml
index 6d42db8..fc6eb55 100644
--- a/.github/workflows/vtest.yml
+++ b/.github/workflows/vtest.yml
@@ -78,7 +78,7 @@
       run: env ${{ matrix.ssl }} scripts/build-ssl.sh
     - name: Build WURFL
       if: ${{ contains(matrix.FLAGS, 'USE_WURFL=1') }}
-      run: make -C contrib/wurfl
+      run: make -C addons/wurfl/dummy
     - name: Compile HAProxy with ${{ matrix.CC }}
       run: |
         make -j$(nproc) all \