ncurses 5.6 - patch 20070127

ncurses 5.6 - patch 20070127

+ improve fix for FreeBSD gnu/98975, to allow for null pointer passed
  to tgetent() (report by Rong-en Fan).
+ update tack/HISTORY and tack/README to tell how to build it after
  it is removed from the ncurses tree.
+ fix configure check for libtool's version to trim blank lines
  (report by sci-fi@hush.ai).
+ review/eliminate other original-file artifacts in cursesw.cc, making
  its license consistent with ncurses.
+ use ncurses vw_scanw() rather than reading into a fixed buffer in
  the c++ binding for scanw() methods.
+ eliminate fixed-buffer vsprintf() calls in c++ binding.