multitable inside deftypefun does not respect margin

[Bruno Haible]

Hi,

When @multitable is used inside @deftypefun, it produces output that extends
heavily into the right margin, in TeX mode. I'm using texinfo.tex version
2008-04-18.10.

This is the piece of input (part of the GNU libunistring doc):

========================================================================

@deftypefun ucs4_t uc_totitle (ucs4_t @var{uc})
Returns the titlecase mapping of the Unicode character @var{uc}.

The titlecase mapping of a character is to be used when the character should
look like upper case and the following characters are lower cased.

For most characters, this is the same as the uppercase mapping.  There are
only few characters where the title case variant and the uuper case variant
are different.  These characters occur in the Latin writing of the Serbian
and Croatian languages.

@multitable @columnfractions .33 .33 .33
@headitem Lower case @tab Title case @tab Upper case
@item LATIN SMALL LETTER LJ
 @tab LATIN CAPITAL LETTER L WITH SMALL LETTER J
 @tab LATIN CAPITAL LETTER LJ
@item LATIN SMALL LETTER NJ
 @tab LATIN CAPITAL LETTER N WITH SMALL LETTER J
 @tab LATIN CAPITAL LETTER NJ
@item LATIN SMALL LETTER DZ
 @tab LATIN CAPITAL LETTER D WITH SMALL LETTER Z
 @tab LATIN CAPITAL LETTER DZ
@item LATIN SMALL LETTER DZ WITH CARON
 @tab LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON
 @tab LATIN CAPITAL LETTER DZ WITH CARON
@end multitable
@end deftypefun

========================================================================

The output in PDF format is as follows: