patch 9.0.0999: memory may leak

Problem:    Memory may leak.
Solution:   Free the sound callback function name if it was allocated.

src/sound.c

@@ -60,6 +60,8 @@ get_sound_callback(typval_T *arg)
 	soundcb->snd_next = first_callback;
 	first_callback = soundcb;
 	set_callback(&soundcb->snd_callback, &callback);
+	if (callback.cb_free_name)
+	    vim_free(callback.cb_name);
     }
     return soundcb;
 }

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    999,
 /**/
     998,
 /**/