@ continuation not working in @def...

[Gavin Smith]

Reporting this bug here as I haven't been getting to it in the last
few days, in case somebody else could look into it.

@ is supposed to be a line continuation character inside @deffn, but
the following gives an error "unexpected @":

@deffn {Public Function} count_records (@var{start}, @
                                                @var{end}, @
                                                @var{record_id_vector} = 0]) 
@end deffn

(From "IWF Metadata Harvester Manual").  I couldn't see what was wrong with
this so I assume there must be a bug in texi2any.