[Simh] idle on VAX with 3.8-1

[Jason Stevens]

I think the new source has some weird issue with sim_timer.c & the
vax_cpu.c with the idle...

# BIN/vax

VAX simulator V3.8-1
sim> set cpu idle=32v
Invalid argument
sim> show cpu
CPU, idle disabled, 16MB, HALT to SIMH
sim> set cpu idle
sim> set cpu idle=32v
Invalid argument
sim> show cpu
CPU, idle enabled=32V, 16MB, HALT to SIMH

however replacing the sim_timer.c from 3.8-0 it works without
complaining.. I haven't dug down enough to find what's exactly going
on but I think it's something in the sim_set_idle* stuff...

more of an FYI..