Log Message:
Changes 5.8:
Interface changes
* turn on _XOPEN_CURSES definition in curses.h.
* change _nc_has_mouse to has_mouse, reflect its use in C++ and Ada95.
* add is_pad and is_subwin functions for opaque access to the WINDOW structure.
* add tiparm, based on review of X/Open Curses Issue 7.

Library Improvements
* add a terminal driver for Windows console, which supports a MinGW port to
  Windows.
* add extended functions which specify the SCREEN pointer for several curses
  functions which use the global SP.
* improve the NCURSES_NO_UTF8_ACS feature by adding a check for an extended
  terminfo capability U8.
* improve performance of tigetstr, etc., by using hashing code from tic.
* add WACS_xxx definitions to wide-character configuration for thick- and
  double-lines.
* modify init_pair to allow caller to create extra color pairs beyond the
  color_pairs limit, which use default colors.

Improvements to Programs
* add tabs program.
* modify tic's -I/-C dump to reformat acsc strings into canonical form (sorted,
  unique mapping).
* add checks in tic for inconsistent cursor-movement controls, and for
  inconsistent printer-controls.
* add special case to _nc_infotocap (used by tic and infocmp) to recognize the
  setaf/setab strings from xterm+256color and xterm+88color, and provide a
  reduced version which works with termcap.