The property `sector_t::special` triggers check for plane difference

[elf-alchemist]

This check was introduced in DSDA's merger of Hexen code, does not match up with vanilla (cl2/3/4) or Chocolate behavior.

This has generated known issue with Eviternity II MAP18 and various maps in TWOGERS

Test wad: texclipfloor.zip

Test setup:

Chocolate -- ❌ does NOT read special when checking difference:

Woof -- ✔️ DOES read special when checking difference:

DSDA -- ✔️ DOES read special when checking difference:

Odamex -- ❌ does NOT read special when checking difference:

Eternity -- ❌ does NOT read special when checking difference:

KEX -- ❌ does NOT read special when checking differencex:

GZDoom -- ❌ does NOT read special when checking difference:

[electricbrass]

This is not about line special, nor specifically about texture clipping. It is about whether sector specials are used when determining if two planes are identical or not.

[elf-alchemist]

This is not about line special, nor specifically about texture clipping. It is about whether sector specials are used when determining if two planes are identical or not.

Fixed the transcription, thank you.