ncurses 6.0 - patch 20170318

ncurses 6.0 - patch 20170318

+ change TERMINAL structure in term.h to make it opaque.  Some
  applications misuse its members, e.g., directly modifying it
  rather than using def_prog_mode().
+ modify utility headers such as tic.h to make it clearer which are
  externals that are used by tack.
+ improve curs_slk.3x in particular its discussion of portability.
+ fix cut/paste in legacy_encoding.3x
+ add prototype for find_pair() to new_pair.3x (report by Branden
  Robinson).
+ fix a couple of broken links in generated man-html documentation.
+ regenerate man-html documentation.