ncurses 6.0 - patch 20171028

ncurses 6.0 - patch 20171028

+ improve man/curs_inwstr.3x, correct end-logic for lib_inwstr.c
  (report by Midolikawa H).
+ fix typo in a few places for "improvements" (patch by Sven Joachim).
+ clear the other half of a double-width character on which a line
  drawing character is drawn.
+ make test/ncurses.c "s" test easier to understand which subtests are
  available; add a "S" wide-character overlap test-screen.
+ modify test/ncurses.c C/c tests to allow for extended color pairs.
+ add endwin() call in error-returns from test/ncurses.c omitted in
  recent redesign of its menu (cf: 20170923).
+ improve install of hashed-db by removing the ".db" file as done for
  directory-tree terminal databases.
+ repair a few overlooked items in include/ncurses_defs from recent
  port/refactoring of test-programs (cf: 20170909).
+ add test/padview.c, to compare pads with direct updates in view.c