ncurses 6.0 - patch 20170401

ncurses 6.0 - patch 20170401

+ minor fixes for vt100+4bsd, e.g., delay in sgr for consistency -TD
+ add smso for env230, to match sgr -TD
+ remove p7/protect from sgr in fbterm -TD
+ drop setf/setb from fbterm; setaf/setab are enough -TD
+ make xterm-pcolor sgr consistent with other capabilities -TD
+ add rmxx/smxx ECMA-48 strikeout extension to tmux and xterm-basic
  (discussion with Nicholas Marriott)
+ add test-programs sp_tinfo and extended_color
+ modify no-leaks code for lib_cur_term.c to account for the tgetent()
  cache.
+ modify setupterm() to save original tty-modes so that erasechar()
  works as expected.  Also modify _nc_setupscreen() to avoid redundant
  calls to get original tty-modes.
+ modify set_curterm() to update ttytype[] data used by longname().
+ modify wattr_set() and wattr_get() to return ERR if win-parameter is
  null, as documented.
+ improve cast used for null-pointer checks in header macros, to
  reduce compiler warnings.
+ modify several functions, using the reserved "opts" parameter to pass
  color- and pair-values larger than 16-bits:
  + getcchar(), setcchar(), slk_attr_set(), vid_puts(), wattr_get(),
    wattr_set(), wchgat(), wcolor_set().
  + Other functions call these with the corresponding altered behavior,
    including chgat(), mvchgat(), mvwchgat(), slk_color_on(),
    slk_color_off(), vid_attr().
+ add new functions for manipulating color- and pair-values larger
  than 16-bits.  These are extended_color_content(),
  extended_pair_content(), extended_slk_color(), init_extended_color(),
  init_extended_pair(), and the corresponding sp-funcs.