ALSA: use non-modal error dialogs

aout_Restart() is quite buggy (IMHO) and restarts the audio output
from the interface thread. Then Qt4 external dialogs are buggy as
they deadlock if called from the interface thread (I cannot find a
direct way to use BlockingQueuedConnection for foreign threads and
DirectConnection for the interface thread).

Until either or both of those bugs are fixed, we cannot use modal
dialog from the audio output.
(cherry picked from commit cbe1cda8765084294b3649fc89ddd63c26dd2f4c)

modules/audio_output/alsa.c

@@ -272,7 +272,7 @@ static void Probe( aout_instance_t * p_aout,
     if( val.i_int <= 0 )
     {
         if( var_GetBool( p_aout->p_libvlc, "alsa-working" ) )
-            dialog_FatalWait( p_aout, "ALSA version problem",
+            dialog_Fatal( p_aout, "ALSA version problem",
                 "VLC failed to re-initialize your sound output device.\n"
                 "Please update alsa-lib to version 1.0.22 or higher "
                 "to fix this issue." );
@@ -289,7 +289,7 @@ static void Probe( aout_instance_t * p_aout,
         if( !var_GetBool( p_aout->p_libvlc, "alsa-broken" ) )
         {
             var_SetBool( p_aout->p_libvlc, "alsa-broken", true );
-            dialog_FatalWait( p_aout, "Potential ALSA version problem",
+            dialog_Fatal( p_aout, "Potential ALSA version problem",
                 "VLC failed to initialize your sound output device (if any).\n"
                 "Please update alsa-lib to version 1.0.24 or higher "
                 "to try to fix this issue." );