(svn r2688) MSVC and Watcom can't handle identical file names in different directories, oh my...

sound/null_s.c

@@ -0,0 +1,11 @@
+#include "stdafx.h"
+#include "openttd.h"
+#include "sound/null_s.h"
+
+static const char *NullSoundStart(const char * const *parm) { return NULL; }
+static void NullSoundStop(void) {}
+
+const HalSoundDriver _null_sound_driver = {
+	NullSoundStart,
+	NullSoundStop,
+};