Emulate "2s middle textures do not animate in v1.2"

[mfrancis95]

Found something that PrBoom+ is doing that Chocolate Doom isn't: https://github.com/coelckers/prboom-plus/blob/969515162c5aebea4ad7a125ee178dcad3d576ad/prboom2/src/r_segs.c#L283C62-L286.

This is also covered in decino's breakdown on complevels: https://youtu.be/XFZFNE0a82w?si=gdkBRDkZ_pZuocXQ&t=731

Looks like a straightforward thing to add in, but it would be good to test this in other versions like 1.4 and see if it was fixed there, because PrBoom+ is using 1.666 as a marker, as well as add this discovery to https://doomwiki.org/wiki/Versions_of_Doom_and_Doom_II.

[tpoppins]

I just tested several versions for this bug. The 1.6 beta still doesn't animate middle tex on 2-sided linedefs, so this bug was fixed only in v1.666.