patch 8.1.1515: memory leak reported for sound when build with EXITFREE

Problem:    Memory leak reported for sound when build with EXITFREE.
Solution:   Free sound stuff when exiting.

Author: brammool

src/misc2.c

@@ -1247,6 +1247,9 @@ free_all_mem(void)
     /* screenlines (can't display anything now!) */
     free_screenlines();
 
+# if defined(FEAT_SOUND)
+    sound_free();
+# endif
 # if defined(USE_XSMP)
     xsmp_close();
 # endif

src/version.c

@@ -777,6 +777,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1515,
 /**/
     1514,
 /**/