Today we updated openttd-useful.zip to change a library to support natural sorting of strings.
If you want to compile upcoming releases/nightlies/trunk you have to update, however if you want to compile OpenTTD before r21340 you will need version 3.4. To be able to compile both OpenTTD revisions before and after r21340 you have to install version 3.4 first and then install version 4.0 over that.

If you do not compile OpenTTD yourself or you are not using Microsoft's compiler you will not be affected.