remove unneeded externs

--- sound.h.orig	2006-06-05 11:52:23 +0400
+++ sound.h	2006-06-05 11:52:45 +0400
@@ -40,8 +40,6 @@
 extern int sound_enabled_ever;
 extern int sound_freq;
 extern int sound_stereo;
-extern int sound_stereo_beeper;
-extern int sound_stereo_ay;
 extern int sound_stereo_ay_abc;
 extern int sound_stereo_ay_narrow;