core: Support memfd transport; bump protocol version

Now that all layers in the stack support memfd blocks, add memfd
support for the daemon's global core mempool. Also introduce
"enable-memfd=" daemon argument and configuration option.

For now, memfd support is an opt-in feature to be activated only
when daemon's enable-memfd= is set to yes.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>

shell-completion/bash/pulseaudio

@@ -500,13 +500,13 @@ _pulseaudio()
                 --realtime= --disallow-module-loading= --disallow-exit= --exit-idle-time=
                 --scache-idle-time= --log-level= -v --log-target= --log-meta= --log-time=
                 --log-backtrace= -p --dl-search-path= --resample-method= --use-pit-file=
-                --no-cpu-limit= --disable-shm= -L --load= -F --file= -C -n'
+                --no-cpu-limit= --disable-shm= --enable-memfd= -L --load= -F --file= -C -n'
     _init_completion -n = || return
 
     case $cur in
         --system=*|--daemonize=*|--fail=*|--high-priority=*|--realtime=*| \
             --disallow-*=*|--log-meta=*|--log-time=*|--use-pid-file=*| \
-            --no-cpu-limit=*|--disable-shm=*)
+            --no-cpu-limit=*|--disable-shm=*|--enable-memfd=*)
             cur=${cur#*=}
             COMPREPLY=($(compgen -W 'true false' -- "$cur"))
             ;;

shell-completion/zsh/_pulseaudio

@@ -690,6 +690,7 @@ _pulseaudio_completion() {
         '--use-pid-file=[create a PID file]:bool:(true false)' \
         '--no-cpu-limit=[do not install CPU load limiter]:bool:(true false)' \
         '--disable-shm=[disable shared memory support]:bool:(true false)' \
+        '--enable-memfd=[enable memfd shared memory support]:bool:(true false)' \
         {-L,--load=}'[load the specified module]:modules:_all_modules' \
         {-F,--file=}'[run the specified script]:file:_files' \
         '-C[open a command line on the running tty]' \