bug: HyperTreeList: window style flags conflict

Hello Andrea

Item text not displayed when using HyperTreeList with style
TR_AUTO_CHECK_CHILD.
The reason is style flags conflict:

  >>> import wx.gizmos
  >>> wx.__version__
  '2.8.10.1'
  >>> import wx.lib.agw.customtreectrl
  >>> wx.lib.agw.customtreectrl.TR_AUTO_CHECK_CHILD
  16384
  >>> wx.gizmos.TR_VIRTUAL
  16384

Thanks,
Oleg

PS: CalculatePositions() before EditLabel() fixes root creation editor
missplace issue, thank You for advice