Since r30397, TAChart has TDataPointHintTool that displays
a hint about chart points on mouseover.
While implementing it, I encountered a few problems:
1) Hint is only displayed if no control key is pressed
(see GetHintInfoAt function), so Shift property of TDataPointHintTool
does not work.
2) To display hint immediately, I have to globally set HintPause to 0,
possibly interfering with other hints.
I suggest to add ShowHintImmediately (or better named) method,
which would display hint regardless of the control keys state and without pause.