tests/test-gendoc-zh_CN.t

tests: splitting test-gendoc.t into per file tests

Localizers can now run test-gendoc-$LOCALE.t instead of
test-gendoc.t.

After this change, test-gendoc.t only checks whether there is *some*
localization for the expected set of languages and no others.

Whenever a locale i18n/$LOCALE.po is added, someone needs
to add test-gendoc-$LOCALE.t

#require docutils gettext

  $ $TESTDIR/check-gendoc zh_CN
  checking for parse errors