Add Screen.sleep() to manually invoke the screensaver

[ambv]

The default screensaver time is 15 minutes. I like to manually turn the screensaver on sooner, which I can do from Maiden by calling:

>> screensaver:event()

To be able to do this, screensaver needs to be a global.

[tehn]

i'd prefer this to be a more explicit function rather than just global a specialized timer.

can you instead make a function screen.sleep() ?

[ambv]

Oh, I like this.

[ambv]

Done!