Export DllMain as native does.

diff --git a/dlls/itss/itss.spec b/dlls/itss/itss.spec
index 46babf3..edc6242 100644
--- a/dlls/itss/itss.spec
+++ b/dlls/itss/itss.spec
@@ -1,5 +1,6 @@
 @ stdcall -private DllCanUnloadNow()
 @ stdcall -private DllGetClassObject(ptr ptr ptr)
 @ stub DllInstall
+@ stdcall DllMain(long long ptr)
 @ stdcall -private DllRegisterServer()
 @ stub DllUnregisterServer