Proposed patch refactors code which converts the result of Tcl call to Python dict. Added new private function _splitdict() which does this in more robust manner.

Also this patch fixes a bug in Treeview.heading(). The heading subcommand of ttk::treeview return options dict in which one key surprisingly was not '-' prefixed.

% ttk::treeview t
% .t heading #0
-text {} -image {} -anchor center -command {} state {}

Current code unconditionally cuts "s" from the "state" key.

>>> from tkinter import ttk
>>> t = ttk.Treeview()
>>> t.heading('#0')
{'anchor': 'center', 'tate': '', 'image': '', 'text': '', 'command': ''}