Small fixups in DSO

- VMS configs had no dso_scheme
- Incorrect return of NULL method.
Reviewed-by: NTim Hudson <tjh@openssl.org>

Configurations/10-main.conf

@@ -1703,6 +1703,7 @@ sub vc_wince_info {
                                    debug   => "/DEBUG/TRACEBACK",
                                    release => "/NODEBUG/NOTRACEBACK"),
         shared_target    => "vms-shared",
+        dso_scheme       => "vms",
         thread_scheme    => "pthreads",
 
         apps_aux_src     => "vms_decc_init.c",

crypto/dso/dso_openssl.c

@@ -66,6 +66,6 @@ static DSO_METHOD dso_meth_null = {
 
 DSO_METHOD *DSO_METHOD_openssl(void)
 {
-    return dso_meth_null();
+    return &dso_meth_null;
 }
 #endif