Added GetConvertStg stub.

dlls/ole32/ole32.spec

@@ -79,7 +79,7 @@ debug_channels (ole relay storage)
  65 stdcall DoDragDrop(ptr ptr long ptr) DoDragDrop
  66 stub EnableHookObject
  67 stdcall GetClassFile(ptr ptr) GetClassFile
- 68 stub GetConvertStg
+ 68 stdcall GetConvertStg(ptr) GetConvertStg
  69 stub GetDocumentBitStg
  70 stdcall GetHGlobalFromILockBytes(ptr ptr) GetHGlobalFromILockBytes
  71 stdcall GetHGlobalFromStream(ptr ptr) GetHGlobalFromStream

dlls/ole32/storage32.c

@@ -6969,3 +6969,8 @@ HRESULT WINAPI OleConvertIStorageToOLESTREAM (
 
     return hRes;
 }
+
+HRESULT WINAPI GetConvertStg(LPGUID guid) {
+    FIXME("(%s), unimplemented stub!\n",debugstr_guid(guid));
+    return E_FAIL;
+}