ncurses 6.4 - patch 20230610

ncurses 6.4 - patch 20230610

+ improve manpages discussing file descriptors in low-level functions.
+ modify flushinp to use file descriptors in SCREEN, rather than from
  TERMINAL, and check if they are for a terminal, like SVr4.
+ modify mcprint to use file descriptor in SCREEN, for consistency.
+ add xterm+focus to foot+base (patch by Daniel Ekloef).
+ correct definition of Charable() for non-wide ncurses library (report
  and test-case by Zbigniew Baniewski).