The following packages should be installed before GNU libunistring is
installed:

* GNU libiconv
  + Not needed on systems with
      - glibc 2.2 or newer, or
      - MacOS X 10.3 or newer, or
      - NetBSD 3.0 or newer.
    But highly recommended on all other systems.
    Needed for character set conversion of strings from/to Unicode.
  + Homepage:
    https://www.gnu.org/software/libiconv/
  + Download:
    https://ftp.gnu.org/gnu/libiconv/
  + If it is installed in a nonstandard directory, pass the option
    --with-libiconv-prefix=DIR to 'configure'.
