Compare two Uniforum style .po files to check that both contain the same
set of msgid strings. The def.po file is an existing PO file with the
translations. The ref.pot file is the last created PO file, or a PO Template
file (generally created by xgettext). This is useful for checking that
you have translated each and every message in your program. Where an exact
match cannot be found, fuzzy matching is used to produce better diagnostics.
Mandatory arguments to long options are mandatory for short options too.