Request: Support scripted constant for [Files] parameter DestName for downloaded files

[Bill Stewart]

I am developing an installer that downloads the latest version of an archive file based on json metadata from GitHub. It would be a nice feature of we could write:

DestName: "{code:GetDownloadFileName}"

For a file we are downloading.

As it is now, we have to use a "generic" file name that isn't very informative for the user as to which file is being downloaded.