Make more of the OLE interface vtables const.

diff --git a/dlls/dmscript/scripttrack.c b/dlls/dmscript/scripttrack.c
index 25af7eb..11905d6 100644
--- a/dlls/dmscript/scripttrack.c
+++ b/dlls/dmscript/scripttrack.c
@@ -75,7 +75,7 @@
 	return ref;
 }
 
-IUnknownVtbl DirectMusicScriptTrack_Unknown_Vtbl = {
+static const IUnknownVtbl DirectMusicScriptTrack_Unknown_Vtbl = {
 	IDirectMusicScriptTrack_IUnknown_QueryInterface,
 	IDirectMusicScriptTrack_IUnknown_AddRef,
 	IDirectMusicScriptTrack_IUnknown_Release
@@ -194,7 +194,7 @@
 	return S_OK;
 }
 
-IDirectMusicTrack8Vtbl DirectMusicScriptTrack_Track_Vtbl = {
+static const IDirectMusicTrack8Vtbl DirectMusicScriptTrack_Track_Vtbl = {
 	IDirectMusicScriptTrack_IDirectMusicTrack_QueryInterface,
 	IDirectMusicScriptTrack_IDirectMusicTrack_AddRef,
 	IDirectMusicScriptTrack_IDirectMusicTrack_Release,
@@ -252,7 +252,7 @@
 	return E_NOTIMPL;
 }
 
-IPersistStreamVtbl DirectMusicScriptTrack_PersistStream_Vtbl = {
+static const IPersistStreamVtbl DirectMusicScriptTrack_PersistStream_Vtbl = {
 	IDirectMusicScriptTrack_IPersistStream_QueryInterface,
 	IDirectMusicScriptTrack_IPersistStream_AddRef,
 	IDirectMusicScriptTrack_IPersistStream_Release,