add xset dpms settings

xinitrc

@@ -13,6 +13,7 @@ type synclient >/dev/null 2>&1 && {
 }
 
 xset s 1800 # go blank after 30 min
+xset dpms 1810 1820 1830        # standby, suspend and off seem to be not different for my environment
 
 unset LC_MESSAGES
 export LANG=ja_JP.utf8