ncurses 6.0 - patch 20170415

+ modify several test programs to use new popup_msgs, adapted from
  help-screen used in test/edit_field.c
+ drop two symbols obsoleted in 2004: _nc_check_termtype, and
  _nc_resolve_uses
+ fix some old copyright dates (cf: 20031025).
+ build-fixes for test/savescreen.c to work with AIX and HPUX.
+ minor fix to configure script, adding a backslash/continuation.
+ extend TERMINAL structure for ABI 6 to store numbers internally as
  integers rather than short, by adding new data for this purpose.
+ more fixes for minor memory-leaks in test-programs.