ncurses 6.2 - patch 20210904

ncurses 6.2 - patch 20210904

+ modify linux3.0 entry to reflect default mapping of shift-tab by
  kbd 1.14 (report by Jan Engelhardt) -TD
+ add historical note to tput, curses-terminfo and curses-color
  manpages based on source-code for SVr2, SVr3 and SVr4.
+ minor grammatical fixes for "it's" vs "its" (report by Nick Black).
+ amend fix for --disable-root-environ (report by Arnav Singh).
+ build-fix for compiling link_test
+ drop symbols GCC_PRINTF and GCC_SCANF from curses.h.in, to simplify
  use (Debian #993179).