ncurses 6.2 - patch 20210320

ncurses 6.2 - patch 20210320

+ improve parameter-checking in tput by forcing it to analyze any
  extended string capability, e.g., as used in the Cs and Ms
  capabilities of the tmux description (report by Brad Town,
  cf: 20200531).
+ remove an incorrect free in the fallback (non-checking) version of
  _nc_free_and_exit (report by Miroslav Lichvar).
+ correct use-ordering in some xterm-direct flavors -TD
+ add hterm, hterm-256color (Mike Frysinger)
+ if the build-time compiler accepts c11's _Noreturn keyword, use that
  rather than gcc's attribute.
+ change configure-check for gcc's noreturn attribute to assume it is
  a prefix rather than suffix, matching c11's _Noreturn convention.
+ add "lint" rule to c++/Makefile, e.g., with cppcheck.