win32u: Avoid calling RtlInitUnicodeString on a static constant.

dlls/win32u/imm.c

@@ -277,12 +277,11 @@ BOOL register_imm_window( HWND hwnd )
     /* Create default IME window */
     if (!thread_data->window_cnt++)
     {
-        UNICODE_STRING class_name, name;
         static const WCHAR imeW[] = {'I','M','E',0};
         static const WCHAR default_imeW[] = {'D','e','f','a','u','l','t',' ','I','M','E',0};
+        UNICODE_STRING class_name = RTL_CONSTANT_STRING( imeW );
+        UNICODE_STRING name = RTL_CONSTANT_STRING( default_imeW );
 
-        RtlInitUnicodeString( &class_name, imeW );
-        RtlInitUnicodeString( &name, default_imeW );
         thread_data->default_hwnd = NtUserCreateWindowEx( 0, &class_name, &class_name, &name,
                                                           WS_POPUP | WS_DISABLED | WS_CLIPSIBLINGS,
                                                           0, 0, 1, 1, 0, 0, 0, 0, 0, 0, 0, FALSE );