access_alsa: abort if snd_pcm_start() returns an error.

Graciously fail if snd_pcm_start() returns an error.

modules/access/alsa.c

@@ -623,7 +623,13 @@ static int OpenAudioDevAlsa( demux_t *p_demux, const char *psz_device )
         goto adev_fail;
     }
 
-    snd_pcm_start( p_sys->p_alsa_pcm );
+    if( snd_pcm_start( p_sys->p_alsa_pcm ) < 0)
+    {
+        msg_Err( p_demux,
+                 "ALSA: failed to start audio interface for use (%s)",
+                 snd_strerror( i_err ) );
+        goto adev_fail;
+    }
 
     return VLC_SUCCESS;