Make s_useOpenAL be CVAR_LATCH

After changing s_useOpenAL the sound needs to be restarted (snd_restart)
for it to take affect.

code/client/snd_main.c

@@ -498,7 +498,7 @@ void S_Init( void )
 		Cmd_AddCommand( "s_stop", S_StopAllSounds );
 		Cmd_AddCommand( "s_info", S_SoundInfo );
 
-		cv = Cvar_Get( "s_useOpenAL", "1", CVAR_ARCHIVE );
+		cv = Cvar_Get( "s_useOpenAL", "1", CVAR_ARCHIVE | CVAR_LATCH );
 		if( cv->integer ) {
 			//OpenAL
 			started = S_AL_Init( &si );