Cleanup thread context initialization code

xtoskrnl/ke/i686/kthread.c

@@ -80,19 +80,13 @@ KepInitializeThreadContext(IN PKTHREAD Thread,
         ThreadFrame->TrapFrame.Dr6 = 0;
         ThreadFrame->TrapFrame.Dr7 = 0;
 
-        /* Set exception list pointer in the trap frame */
-        // ThreadFrame->TrapFrame.ExceptionList = (PEXCEPTION_REGISTRATION_RECORD) - 1;
-
         /* Set DS, ES and SS segments for user mode */
         ThreadFrame->TrapFrame.SegDs |= RPL_MASK;
         ThreadFrame->TrapFrame.SegEs |= RPL_MASK;
         ThreadFrame->TrapFrame.SegSs |= RPL_MASK;
 
-        /* Set debug mark in the trap frame */
-        // ThreadFrame->TrapFrame.DbgMark = 0x8BADF00D;
-
         /* Set user mode thread in the trap frame */
-        // ThreadFrame->TrapFrame.PreviousMode = UserMode;
+        ThreadFrame->TrapFrame.PreviousMode = UserMode;
     }
     else
     {