server: Add get_token_impersonation_level server call for retrieving the impersonation level from a token.

Add tests for GetTokenInformation(TokenImpersonationLevel).
diff --git a/server/request.h b/server/request.h
index 9119ec1..b24d7c7 100644
--- a/server/request.h
+++ b/server/request.h
@@ -326,6 +326,7 @@
 DECL_HANDLER(open_symlink);
 DECL_HANDLER(query_symlink);
 DECL_HANDLER(get_object_info);
+DECL_HANDLER(get_token_impersonation_level);
 
 #ifdef WANT_REQUEST_HANDLERS
 
@@ -548,6 +549,7 @@
     (req_handler)req_open_symlink,
     (req_handler)req_query_symlink,
     (req_handler)req_get_object_info,
+    (req_handler)req_get_token_impersonation_level,
 };
 #endif  /* WANT_REQUEST_HANDLERS */