Rewrote qtGui.setIdleTimeHook so that a) it *only* triggers at idle time and b) it only calls g.idleTimeHookHandler once every g.app.idleTimeDelay msec.
For example, the following script now works::

    ''''Toggle idle-time handling.'''
    if g.app.idleTimeHook:
        g.disableIdleTimeHook()
    else:
        g.enableIdleTimeHook()
Merge branch 'master' of https://github.com/leo-editor/leo-editor