message: Use as default source code charset
  If not provided, xgettext falls back to ASCII. These days, is the
  most likely really used charset and a strict superset of ASCII, so this
  change can only make things better, not worse.
diff: @@ -141,7 +141,7 @@ public:
  QuoteCmdlineArg(outfile),
  QuoteCmdlineArg(basepath),
  QuoteCmdlineArg(filelist.GetName()),
  - QuoteCmdlineArg(sourceSpec.Charset)
  + QuoteCmdlineArg(!sourceSpec.Charset.empty() ? sourceSpec.Charset : "UTF-8")
  );
  for (auto& kw: sourceSpec.Keywords)
  