this adds some IWAD file names to search for, especially renamed files from the BFG Edition and Freedoom. The list is taken from ZDoom modulo the IWADs that prboom-plus does not support and sligthly re-arranged.
I'm not sure about ordering. I think bfg iwads should be somewhere after standard iwads
applied with different order
Literally on the same day you applied this patch, the Freedoom project decided to rename their IWAD names to freedoom1.wad and freedoom2.wad, respectively . So, please replace freedoom.wad->freedoom2.wad and freedoomu.wad->freedoom1.wad, thanks!