readme: ctrl alt del link to so answers

cirosantilli · cirosantilli · commit fafcf0663dce · 2018-05-20T15:53:51.000+01:00
diff --git a/README.adoc b/README.adoc
@@ -3244,6 +3244,9 @@ sendkey shift-pgdown
 
 ===== Ctrl Alt Del
 
+* https://superuser.com/questions/193652/does-linux-have-a-ctrlaltdel-equivalent/1324415#1324415
+* https://unix.stackexchange.com/questions/42573/meaning-and-commands-for-ctrlaltdel/444969#444969
+
 Reboot guest:
 
 ....
