* Some platforms like Ubuntu actually ship widechar and non-widechar versions
  of ncurses with different pkg-config files.
  Other platforms like FreeBSD will ship an "ncursesw" and "ncurses" pkg-config file
  but both point to the same wide-char library anyway.
* Currently we are not using wide-char APIs to ensure maximum compatibility even with
  embedded systems where ncurses might be built without widechar support.
  But in order to handle Unicode correctly, we still need to link against the widechar version
  of ncurses (if available).
* Compilation on platforms without a widechar ncurses is now handled by the common
  AC_CHECK_LIB() fallback (which might actually find a widechar version anyway if it just
  didn't install the pkg-config file).
  If necessary, we could also check for the "ncurses" package if "ncursesw" is not found.
* This fixes Unicode display and input on Ubuntu.

* You no longer have to copy contrib/scintilla, contrib/scinterm and contrib/lexilla
  manually to the build directory.
* It turns out, that Scintilla/Lexilla was supporting this since 2016.
  Scintilla allows pointing to a source directory (srdir) and Lexilla to a binary directory (DIR_O).
* For Scinterm I opened a pull request in order to add srcdir/basedir variables:
  https://github.com/orbitalquark/scinterm/pull/21
* `make distcheck` is therefore now also fixed.
* The FreeBSD package is now allowed to build out of source.
  I haven't tested it yet.
* See also https://github.com/ScintillaOrg/lexilla/issues/266

* dh_testdir would sometimes cause problems on the PPA servers,
  so we replaced it with an empty rule.
* We need to define the binary-arch and binary-indep targets
  in order to recurse into the correct subdirectories.
  I do not understand why this always worked on the Github runner
  and sometimes even on the PPA servers.
  Unfortunately, we cannot just call `dh binary-arch -B... -p...`
  since that would call `dh_install -a` which overrides any `-p` (package),
  thus trying to install the curses binaries from the Gtk build directory
  and vice versa.

* This resolves must lintian warnings and errors.

* Useful for packaging on platforms where we can only build from tarballs (FreeBSD)
* I don't know whether it's always safe and correct to install this file into $DATADIR/applications,
  so the file is only distributed but not installed yet.
* It contains a hardcoded binary name "gsciteco". This could actually differ
  depending on the concrete --program-prefix and it would be good to include the exact
  installation path.
  This however is not possible as long as we do not install this file.

* fixed some Debian lintian warnings