Untranslatable message

[Göran Uddeborg]

In the function muscle_percent_define_insert in muscle_tab.c there is
this code:

      warn_at (variable_loc, _("%s `%s' redefined"),
               "%define variable", variable);

This gets hard to translate, since "%define variable" isn't available
for translation.  Is there some problem having this code instead?

      warn_at (variable_loc, _("%%define variable `%s' redefined"),
               variable);