Wolf4sdl game data

[s1eve-mcdichae1]

In the Wolfenstein 3D docs we are instructed to rename three files from the Spear of Destiny expansion from extension .sod to .sd1. (Presumably because the source files are available in both forms and so no one way is going to work in the scripts without some renaming.)

But then the install script still checks for the old .sod file when determining whether to download the shareware version. If we rename our registered version files as instructed, then the shareware will still be downloaded because the filenames don't match.

PR #3445 fixes this to search for the correct file. I also added a function that should automatically rename the .sod files so we don't have to do it manually.

[cmitu]

If you already opened a PR for it, why open a separate issue ? One is enough.