ncurses 6.1 - patch 20191221

ncurses 6.1 - patch 20191221

+ correct pathname used in Ada95 sample programs for explain.txt, to
  work with test-packages.
+ improve tracemunch:
  + keep track of TERMINAL* values
  + if tracing was first turned on after initialization, attempt to
    show distinct screen, window and terminal names anyway.
+ ensure that GCC_NORETURN is defined in term.h, because the prototype
  for exit_terminfo() uses it (report by Werner Fink).