gettext*: update to 0.20.2

Version 0.20.2 - April 2020

* Improvements for maintainers:
  - A dependency bug in po/Makefile.in.in has been fixed.

* Programming languages support:
  - Shell:
    o The programs 'gettext', 'ngettext', when invoked with option -e, now
      expand '\\' and octal escape sequences, instead of swallowing them.
      (Bug present since the beginning.)
    o xgettext now recognizes 'gettext' program invocations with the '-e'
      option, such as
        gettext -e 'some\nstring\n'
  - Python:
    xgettext now assumes a Python source file is in UTF-8 encoding by default,
    as stated in PEP 3120.
  - Desktop Entry:
    The value of the 'Icon' property is no longer extracted into the POT file
    by xgettext.  The documentation explains how to localize icons.

* Runtime behaviour:
  - The interpretation of the language preferences on macOS has been improved,
    especially in the case where a system locale does not exist for the
    combination of the selected primary language and the selected territory.
  - Fixed a multithread-safety bug on Cygwin and native Windows.

(wiz)