- removed STACK_ARGS.

The only reason this even existed was that ZDoom's original VC projects used __fastcall. The CMake generated project do not, they stick to __cdecl.
Since no performance gain can be seen by using __fastcall the best course of action is to just remove all traces of it from the source and forget that it ever existed.

src/p_user.cpp

@@ -540,7 +540,7 @@ void PClassPlayerPawn::DeriveData(PClass *newclass)
 	}
 }
 
-static int STACK_ARGS intcmp(const void *a, const void *b)
+static int intcmp(const void *a, const void *b)
 {
 	return *(const int *)a - *(const int *)b;
 }