extract_translations - auxiliary tool that extracts lines to be translated
from ejabberd source tree.

Building:
    erlc extract_translations.erl

Invoking 1:
    erl -noinput -s extract_translations -extra dirname message_file

    where dirname is the directory "src" in ejabberd's source tree root,
    message_file is a file with translated messages (src/msgs/*.msg).

    Result is a list of messages from source files which aren't contained in
    message file.

Invoking 2:
    erl -noinput -s extract_translations -extra -unused dirname message_file

    Result is a list of messages from message file which aren't in source
    files anymore.