Add the :class:`curses.complexchar` type, representing a styled character
cell (text, attributes and color pair), and the :mod:`curses` window methods
:meth:`~curses.window.in_wch` and :meth:`~curses.window.getbkgrnd` that return
one.  The character-cell methods (:meth:`~curses.window.addch`,
:meth:`~curses.window.bkgd`, :meth:`~curses.window.border`,
:meth:`~curses.window.hline` and others) now also accept a
:class:`~curses.complexchar`.  This works whether or not Python was built
against a wide-character-aware curses library; on a narrow build a cell holds a
single character representable as one byte in the window's encoding.
