Some functions to use with header controls in AHK GUIs.

• HD_EX_Insert()
  Inserts a new item into a header control.
• HD_EX_CreateHDITEM()
  Creates a HDITEM structure - for internal use!!!
• HD_EX_Delete()
  Deletes the specified item from a header control.
• HD_EX_GetCount()
  Gets the count of the items in a header control.
• HD_EX_GetData()
  Gets the application-defined data (lParam) of the specified item.
• HD_EX_GetFormat()
  Gets the format of the specified item.
• HD_EX_GetRect()
  Gets the bounding rectangle for a given item in a header control.
• HD_EX_SetBitmap()
  Assigns a bitmap to the specified item.
• HD_EX_SetBitmapMargin()
  Sets the width of the margin, specified in pixels, of a bitmap in a header control.
• HD_EX_SetData()
  Sets application-defined data (lParam) of the specified item.
• HD_EX_SetFormat()
  Sets the format of the specified item.
• HD_EX_SetImage()
  Sets an image from the header's image list for the specified item.
• HD_EX_SetImageList()
  Assigns an image list to a header control.