This platform had no emulation-related changes.
Remove code for IRIX40, INDIGO definitions.
In disk code, simplify a chain of #ifdef's around fsync handling.
Ultrix hasn't seen an update since 1995 and the DEC3100 hardware
that this was originally written for was released in 1989.
It isn't likely that anyone has Ultrix running on hardware where
they would also want to run this.
