ncurses 6.1 - patch 20190121

ncurses 6.1 - patch 20190121

+ add a check in test/configure to work around non-ncurses termcap.h
  file in Slackware.
+ corrected flag for "seq" method of db 1.8.5 interface, needed by toe
  on some of the BSDs.
+ updated "string-hacks" feature.
+ minor improvements to manpage typography.
+ corrected conditionally-compiled limit on color pairs (report by
  "Hudd").
+ add -x option to test/pair_content, test/color_content for testing
  init_extended_pair, extended_pair_content, init_extended_color,
  extended_color_content
+ add -p option to test/pair_content, test/color_content to show the
  return values from the tested functions.
+ improve manual page curs_color.3x discussion of error returns and
  extensions.
+ add O_INPUT_FIELD extension to form library (patch by Leon Winter).
+ override/suppress --enable-db-install if --disable-database configure
  option was given.
+ change a too-large terminal entry in tic from a fatal error to a
  warning (prompted by discussion with Gabriele Balducci).