Lock X11 display until password is entered -- GL version

 xlock locks the X server till the user enters his/her password at the
 keyboard. While xlock is running, all new server connections are
 refused. The mouse cursor is turned off. The screen is blanked and a
 changing pattern is put on the screen. If a key or a mouse button is
 pressed then the user is prompted for the password of the user who
 started xlock.
 .
 This version is built with graphical modes. The companion package
 xlockmore does not contain them. This is the only difference between
 the two packages.