The instance-on-demand didn't really work, since we needed explicit
control over this object's destruction to ensure the timer is stopped
when launching an application. And trying to combine getInstance() with
explicit external delete was just ugly.
Use nullptr instead of NULL, evaluate pointer as bool where possible.
Declare the timer callback as a friend function so the methods it uses
can stay private.
Initialize screenState to false; was uninitialized which means that
an initially blanked screen might not be unblanked.
Force screen enable in constructor instead of when timeout is set.
Add removeScreenTimer method.
Include C++-ified versions of the C headers.
