get_pixmap_icon_from_icon_win rewritten
The function get_pixmap_icon_from_icon_win() is now rewritten.
This function now creates the icon using the function get_window_image_from_x11(),
using itself as Window and updates the icon using icon_update_pixmap().
At this point the Pixmap is only the icon background. Now we must put inside the
dockapp, in the correct position. Then the funcion get the dock application size,
(the max size is wPreferences.icon_size, because get_window_image_from_x11() checks
the valid size), checks if the icon has title and then reparents the dockapp to put
it inside the icon.
This patch includes a lot of comments to better understand the code.