All VAX: Fix idle/inifinite loop detection for instructions with side effects

Recent enhancements to idle/infinite loop detection generalized handling
of detecting 'loop to self' cases.  This was done without considering that
some instructions have side effects (i.e. change other state like the stack
pointer) and thus aren't merely loop to self cases.

This problem was reported in #315

VAX/vax_cpu.c

@@ -2279,7 +2279,7 @@ for ( ;; ) {
     case RSB:
         temp = Read (SP, L_LONG, RA);                   /* get top of stk */
         SP = SP + 4;                                    /* incr stk ptr */
-        JUMP (temp);
+        JUMP_ALWAYS (temp);
         if (sim_switches & SWMASK ('R')) {
             if (step_out_nest_level <= 0)
                 ABORT (SCPE_STEP);