Fix instruction cycle cost assertion check

my_modules/pcjs-client/lib/cpu.js

@@ -1016,7 +1016,10 @@ CPU.prototype.setBurstCycles = function(nCycles)
         var nDelta = this.nStepCycles - nCycles;
         /*
          * NOTE: If nDelta is negative, we will actually be increasing nStepCycles and nBurstCycles.
+         * Which is OK, but if we're also taking snapshots of the cycle counts, to make sure that instruction
+         * costs are being properly assessed, then we need to update nSnapCycles as well.
          */
+        if (DEBUG) this.nSnapCycles -= nDelta;
         this.nStepCycles -= nDelta;
         this.nBurstCycles -= nDelta;
         return true;

my_modules/pcjs-client/lib/x86opxx.js

@@ -2823,7 +2823,9 @@ var X86OpXX = {
         var nInt = this.getIPByte();
         if (this.checkInterruptNotify(nInt)) {
             X86Help.opHelpINT.call(this, nInt, null, 0);
+            return;
         }
+        this.nStepCycles--;     // we don't need to assess the full cost of nOpCyclesInt, but we need to assess something...
     },
     /**
      * @this {X86CPU}