userstudy: split up button press/release handling

A delayed release event is the reason why the focus is sometimes still on the
main window, not on the dialog box.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
userstudy: move state transition to button release handling

If the button is still down when the dialog is run, the focus is on the old
window and the new dialog is out-of-focus. Splitting up press/release handling
and the state transitions accordingly fixes that.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>