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/.travis.yml b/.travis.yml
index 645f7e6..db114b7 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -11,7 +11,7 @@
 
 env:
   global:
-    - FLAGS="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"
+    - FLAGS="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"
     - TMPDIR=/tmp
     - FIFTYONEDEGREES_SRC="addons/51degrees/dummy/pattern"
     - DEBUG_OPTIONS="DEBUG_STRICT=1"
@@ -60,7 +60,7 @@
   - os: linux
     if: type == cron
     compiler: clang
-    env: TARGET=linux-glibc FLAGS="USE_SLZ=1 USE_PCRE2=1 USE_PCRE2_JIT=1 USE_LUA=1 USE_OPENSSL=1 USE_SYSTEMD=1 USE_WURFL=1 WURFL_INC=contrib/wurfl WURFL_LIB=contrib/wurfl USE_51DEGREES=1" CC=clang-9
+    env: TARGET=linux-glibc FLAGS="USE_SLZ=1 USE_PCRE2=1 USE_PCRE2_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_51DEGREES=1" CC=clang-9
     before_script:
       - git clone https://github.com/wtarreau/libslz
       - cd libslz && make && make PREFIX=${HOME}/opt install && cd ..
@@ -81,7 +81,7 @@
 
 script:
   - if [ "${CC%-*}"  = "clang" ]; then export FLAGS="$FLAGS USE_OBSOLETE_LINKER=1" DEBUG_CFLAGS="-g -fsanitize=address" LDFLAGS="-fsanitize=address" ASAN_OPTIONS="log_path=asan.log"; fi
-  - make -C contrib/wurfl
+  - make -C addons/wurfl/dummy
   - make -j3 CC=$CC CPU_CFLAGS.generic="-O1" V=1 ERR=1 TARGET=$TARGET $FLAGS DEBUG_CFLAGS="$DEBUG_CFLAGS" LDFLAGS="$LDFLAGS" ADDLIB="$ADDLIB" SSL_LIB="$SSL_LIB" SSL_INC="$SSL_INC" SLZ_LIB="$SLZ_LIB" SLZ_INC="$SLZ_INC" 51DEGREES_SRC="$FIFTYONEDEGREES_SRC" EXTRA_OBJS="$EXTRA_OBJS" $DEBUG_OPTIONS
   - ./haproxy -vv
   - if [ "${TRAVIS_OS_NAME}" = "linux" ]; then ldd haproxy; fi