Create conversion tools for language files

Create conversion tools for language files

A shell script "lng2po.sh" is provided, to apply the translation given
in a WinBoard .lng file to "xboard.pot", in order to generate a
"language.po" file containing translations for all strings for which
the .lng file had a translation. It makes use of a file "metascript",
which is the ed script used to turn the .lng file in an ed script to
turn the .pot into .po. For example, the command "./lng2po.sh
espa?ol.lng" will create a file "language.po", which can be renamed to
"es.po".
****************************** WARNING ********************************
  Note that the lng2po script does a "recode" that assumes the given
.lng file is encoded in latin-1. This means it canot be used without
modification for the Vietnamese and Chinese translation; you would have
to replace latin-1 by the applicable encoding first (CP1258 / BG2312 /
BIG5).